diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/config/LoanRequestToLoanConverter.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/config/LoanRequestToLoanConverter.java
index 3a4a860..8964171 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/config/LoanRequestToLoanConverter.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/config/LoanRequestToLoanConverter.java
@@ -12,8 +12,6 @@ public Loan convert(LoanRequest source) {
         return Loan.builder()
                 .bookId(source.getBookId())
                 .clientId(source.getClientId())
-                .loanDate(source.getLoanDate())
-                .dueDate(source.getDueDate())
                 .returnDate(source.getReturnDate())
                 .isReturned(source.getIsReturned())
                 .renewalCount(source.getRenewalCount())
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/controller/LoansController.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/controller/LoansController.java
index a596104..6aa492b 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/controller/LoansController.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/controller/LoansController.java
@@ -1,12 +1,18 @@
 package net.unir.missi.desarrollowebfullstack.bookabook.operador.controller;
 
+import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.Parameter;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions.BadParametersException;
+import net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions.EntityInvalidOperationException;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions.EntityNotFoundException;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api.LoanRequest;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api.LoanResponse;
+import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.sql.Loan;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.service.LoanService;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -14,7 +20,9 @@
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
+import java.time.LocalDate;
 import java.util.*;
+import java.util.logging.Logger;
 
 @RestController
 @RequiredArgsConstructor
@@ -24,20 +32,27 @@ public class LoansController {
     private final LoanService service;
 
     @GetMapping("/loans")
+    @Operation(
+            operationId = "Obtener préstamos",
+            description = "Operacion de lectura",
+            summary = "Se devuelve una lista de todos los préstamos almacenados en la base de datos.")
+    @ApiResponse(
+            responseCode = "200",
+            content = @Content(mediaType = "application/json", schema = @Schema(implementation = Loan.class)))
     public ResponseEntity<List<LoanResponse>> getLoans(
-            @Parameter(name="bookId", example = "")
+            @Parameter(name="bookId", description = "Id del Libro préstado")
             @RequestParam(required = false) Long bookId,
-            @Parameter(name="clientId", example = "")
+            @Parameter(name="clientId", description = "Id del Cliente al que se le realizó el préstamo")
             @RequestParam(required = false) Long clientId,
-            @Parameter(name="loanDate", example = "")
-            @RequestParam(required = false)Date loanDate,
-            @Parameter(name="returnDate", example = "")
-            @RequestParam(required = false)Date returnDate,
-            @Parameter(name="dueDate", example = "")
-            @RequestParam(required = false)Date dueDate,
-            @Parameter(name="isReturned", example = "")
+            @Parameter(name="loanDate", description = "Fecha de registro del préstamo")
+            @RequestParam(required = false) LocalDate loanDate,
+            @Parameter(name="returnDate", description = "Fecha en que el libro fue devuelto")
+            @RequestParam(required = false)LocalDate returnDate,
+            @Parameter(name="dueDate", description = "Fecha de vencimiento del préstamo")
+            @RequestParam(required = false)LocalDate dueDate,
+            @Parameter(name="isReturned", description = "Indica si el libro ha sido devuelto")
             @RequestParam(required = false)Boolean isReturned,
-            @Parameter(name="renewalCount", example = "")
+            @Parameter(name="renewalCount", description = "Cantidad de renovaciones del préstamo")
             @RequestParam(required = false)Integer renewalCount
             ) {
 
@@ -61,6 +76,17 @@ public ResponseEntity<List<LoanResponse>> getLoans(
     }
 
     @GetMapping("/loans/{id}")
+    @Operation(
+            operationId = "Obtener un préstamo",
+            description = "Operacion de lectura",
+            summary = "Se devuelve un préstamo a partir de su identificador.")
+    @ApiResponse(
+            responseCode = "200",
+            content = @Content(mediaType = "application/json", schema = @Schema(implementation = Loan.class)))
+    @ApiResponse(
+            responseCode = "404",
+            content = @Content(mediaType = "application/json", schema = @Schema()),
+            description = "No se ha encontrado el préstamo con el identificador indicado.")
     public ResponseEntity<LoanResponse> getLoan(@PathVariable String id) {
         try
         {
@@ -82,6 +108,25 @@ public ResponseEntity<LoanResponse> getLoan(@PathVariable String id) {
     }
 
     @PostMapping("/loans")
+    @Operation(
+            operationId = "Crear un préstamo",
+            description = "Operacion de escritura",
+            summary = "Se crea un préstamo a partir de sus datos.",
+            requestBody = @io.swagger.v3.oas.annotations.parameters.RequestBody(
+                    description = "Datos del préstamo a crear.",
+                    required = true,
+                    content = @Content(mediaType = "application/json", schema = @Schema(implementation = LoanRequest.class))))
+    @ApiResponse(
+            responseCode = "201",
+            content = @Content(mediaType = "application/json", schema = @Schema(implementation = LoanResponse.class)))
+    @ApiResponse(
+            responseCode = "400",
+            content = @Content(mediaType = "application/json", schema = @Schema()),
+            description = "Datos incorrectos introducidos.")
+    @ApiResponse(
+            responseCode = "404",
+            content = @Content(mediaType = "application/json", schema = @Schema()),
+            description = "Id del Libro O Id del Cliente no existen.")
     public ResponseEntity<LoanResponse> addLoan(@RequestBody LoanRequest loanRequest) {
         try
         {
@@ -100,13 +145,28 @@ public ResponseEntity<LoanResponse> addLoan(@RequestBody LoanRequest loanRequest
         {
             return ResponseEntity.badRequest().build();
         }
+        catch(EntityInvalidOperationException e) {
+            return ResponseEntity.badRequest().build();
+        }
         catch (Exception e)
         {
+            Logger.getGlobal().warning("Error: " +  e.getMessage());
             return ResponseEntity.internalServerError().build();
         }
     }
 
     @DeleteMapping("/loans/{id}")
+    @Operation(
+            operationId = "Eliminar un préstamo",
+            description = "Operacion de escritura",
+            summary = "Se elimina un préstamo a partir de su identificador.")
+    @ApiResponse(
+            responseCode = "200",
+            content = @Content(mediaType = "application/json", schema = @Schema(implementation = LoanResponse.class)))
+    @ApiResponse(
+            responseCode = "404",
+            content = @Content(mediaType = "application/json", schema = @Schema()),
+            description = "No se ha encontrado el préstamo con el identificador indicado.")
     public ResponseEntity<LoanResponse> deleteLoan(@PathVariable String id) {
         try
         {
@@ -123,14 +183,30 @@ public ResponseEntity<LoanResponse> deleteLoan(@PathVariable String id) {
     }
 
     @PatchMapping("/loans/{id}")
+    @Operation(
+            operationId = "Modificar parcialmente un préstamo",
+            description = "RFC 7386. Operacion de escritura",
+            summary = "RFC 7386. Se modifica parcialmente un préstamo.",
+            requestBody = @io.swagger.v3.oas.annotations.parameters.RequestBody(
+                    description = "Datos del préstamo a modificar.",
+                    required = true,
+                    content = @Content(mediaType = "application/merge-patch+json", schema = @Schema(implementation = LoanRequest.class))))
+    @ApiResponse(
+            responseCode = "200",
+            content = @Content(mediaType = "application/json", schema = @Schema(implementation = LoanResponse.class)))
+    @ApiResponse(
+            responseCode = "400",
+            content = @Content(mediaType = "application/json", schema = @Schema()),
+            description = "Datos incorrectos introducidos.")
     public ResponseEntity<LoanResponse> patchLoan(@RequestBody LoanRequest loanRequest, @PathVariable String id) {
         try
         {
+            Logger.getGlobal().warning("Entra al controller" + loanRequest);
             if (loanRequest == null)
             {
                 return ResponseEntity.badRequest().build();
             }
-            LoanResponse newLoan = this.service.modifyLoan(loanRequest, Long.valueOf(id));
+            LoanResponse newLoan = this.service.modifyLoan(loanRequest.getIsReturned(), Long.valueOf(id));
             return ResponseEntity.status(HttpStatus.CREATED).body(newLoan);
         }
         catch (EntityNotFoundException e)
@@ -147,7 +223,18 @@ public ResponseEntity<LoanResponse> patchLoan(@RequestBody LoanRequest loanReque
         }
     }
 
-    @GetMapping("/loans/client/{clientId}")
+    @GetMapping("/clients/{clientId}/loans")
+    @Operation(
+            operationId = "Obtener los préstamos de un cliente.",
+            description = "Operacion de lectura",
+            summary = "Se devuelve una lista de préstamos relacionados a un cliente.")
+    @ApiResponse(
+            responseCode = "200",
+            content = @Content(mediaType = "application/json", schema = @Schema(implementation = LoanResponse.class)))
+    @ApiResponse(
+            responseCode = "404",
+            content = @Content(mediaType = "application/json", schema = @Schema()),
+            description = "No se han encontrado préstamos con el identificador de clienteindicado.")
     public ResponseEntity<List<LoanResponse>> getLoanByClientId(@PathVariable String clientId) {
         try
         {
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/exceptions/EntityInvalidOperationException.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/exceptions/EntityInvalidOperationException.java
new file mode 100644
index 0000000..e36cab1
--- /dev/null
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/exceptions/EntityInvalidOperationException.java
@@ -0,0 +1,7 @@
+package net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions;
+
+import jakarta.ws.rs.NotAllowedException;
+
+public class EntityInvalidOperationException  extends RuntimeException {
+    public EntityInvalidOperationException(String errorMessage, Throwable err) { super(errorMessage, err); }
+}
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanDto.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanDto.java
index 24cf40c..20d9b2c 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanDto.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanDto.java
@@ -2,6 +2,7 @@
 
 import lombok.*;
 
+import java.time.LocalDate;
 import java.util.Date;
 
 @Getter
@@ -13,9 +14,9 @@
 public class LoanDto {
     private Long bookId;
     private Long clientId;
-    private Date loanDate;
-    private Date returnDate;
-    private Date dueDate;
+    private LocalDate loanDate;
+    private LocalDate returnDate;
+    private LocalDate dueDate;
     private Boolean isReturned;
     private Integer renewalCount;
 }
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanRequest.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanRequest.java
index 3174e37..defea43 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanRequest.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanRequest.java
@@ -1,6 +1,7 @@
 package net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api;
 import lombok.*;
 
+import java.time.LocalDate;
 import java.util.Date;
 
 @Getter
@@ -12,9 +13,7 @@
 public class LoanRequest {
     private Long bookId;
     private Long clientId;
-    private Date loanDate;
-    private Date returnDate;
-    private Date dueDate;
-    private Boolean isReturned;
-    private Integer renewalCount;
+    private LocalDate returnDate = null;
+    private Boolean isReturned = false;
+    private Integer renewalCount = 0;
 }
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanResponse.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanResponse.java
index d40fc88..1121931 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanResponse.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/api/LoanResponse.java
@@ -2,6 +2,7 @@
 
 import lombok.*;
 
+import java.time.LocalDate;
 import java.util.Date;
 
 @Getter
@@ -14,9 +15,9 @@ public class LoanResponse {
     private Long id;
     private Long bookId;
     private Long clientId;
-    private Date loanDate;
-    private Date returnDate;
-    private Date dueDate;
+    private LocalDate loanDate;
+    private LocalDate returnDate;
+    private LocalDate dueDate;
     private Boolean isReturned;
     private Integer renewalCount;
 }
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/sql/Loan.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/sql/Loan.java
index 9f15221..9962fbe 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/sql/Loan.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/model/sql/Loan.java
@@ -1,5 +1,6 @@
 package net.unir.missi.desarrollowebfullstack.bookabook.operador.model.sql;
 
+import java.time.LocalDate;
 import java.util.Date;
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
@@ -32,11 +33,11 @@ public class Loan {
     @Column(name = "clientId")
     private Long clientId;
     @Column(name = "loanDate")
-    private Date loanDate;
+    private LocalDate loanDate;
     @Column(name = "returnDate")
-    private Date returnDate;
+    private LocalDate returnDate;
     @Column(name = "dueDate")
-    private Date dueDate;
+    private LocalDate dueDate;
     @Column(name = "isReturned")
     private Boolean isReturned;
     @Column(name = "renewalCount")
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanJpaRepository.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanJpaRepository.java
index 646cbab..7feb005 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanJpaRepository.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanJpaRepository.java
@@ -10,4 +10,6 @@
 @Repository
 public interface LoanJpaRepository extends JpaRepository<Loan, Long>, JpaSpecificationExecutor<Loan> {
     List<Loan> findByClientId(Long clientId);
+    List<Loan> findByBookIdAndIsReturned(Long bookId, boolean isRturned);
+
 }
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanRepository.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanRepository.java
index 24a1fed..4f40afc 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanRepository.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/repository/LoanRepository.java
@@ -9,6 +9,7 @@
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Repository;
 
+import java.time.LocalDate;
 import java.util.Date;
 import java.util.List;
 import java.util.Optional;
@@ -26,6 +27,7 @@ public LoanRepository(LoanJpaRepository loanJpaRepository) {
     public List<Loan> findAll() { return loanJpaRepository.findAll(); }
     public Loan findById(Long id) { return loanJpaRepository.findById(id).orElse(null); }
     public List<Loan> findByClientId(Long clientId){ return loanJpaRepository.findByClientId(clientId); }
+    public List<Loan> findByBookIdAndIsReturned(Long bookId, boolean isRturned){ return loanJpaRepository.findByBookIdAndIsReturned(bookId, isRturned); }
     public Loan save(Loan loan){ return loanJpaRepository.save(loan); }
     public Loan delete(Loan loan)
     {
@@ -34,7 +36,7 @@ public Loan delete(Loan loan)
         return l.get();
     }
 
-    public List<Loan> search(Long bookId, Long clientId, Date loanDate, Date returnDate, Date dueDate, Boolean isReturned, Integer renewalCount) {
+    public List<Loan> search(Long bookId, Long clientId, LocalDate loanDate, LocalDate returnDate, LocalDate dueDate, Boolean isReturned, Integer renewalCount) {
         SearchCriteria<Loan> spec = new SearchCriteria<>();
 
         if(bookId != null) {
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/ILoanService.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/ILoanService.java
index 430fb72..a0976f8 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/ILoanService.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/ILoanService.java
@@ -3,16 +3,17 @@
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api.LoanRequest;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api.LoanResponse;
 
+import java.time.LocalDate;
 import java.util.Date;
 import java.util.List;
 
 public interface ILoanService {
     // CRUD
-    List<LoanResponse> getAllLoans(Long bookId, Long clientId, Date loanDate, Date returnDate, Date dueDate, Boolean isReturned, Integer renewalCount);
+    List<LoanResponse> getAllLoans(Long bookId, Long clientId, LocalDate loanDate, LocalDate returnDate, LocalDate dueDate, Boolean isReturned, Integer renewalCount);
     LoanResponse createLoan(LoanRequest request);
     LoanResponse getLoanById(Long id);
     LoanResponse modifyAllLoanData(LoanRequest loan, Long id);
-    LoanResponse modifyLoan(LoanRequest loan, Long id);
+    LoanResponse modifyLoan(boolean isReturned, Long id);
     LoanResponse deleteLoan(String id);
 
     // SPECIALIZATIONS
diff --git a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/LoanService.java b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/LoanService.java
index 2bf495b..b96f39d 100644
--- a/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/LoanService.java
+++ b/src/main/java/net/unir/missi/desarrollowebfullstack/bookabook/operador/service/LoanService.java
@@ -7,6 +7,7 @@
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.config.LoanRequestToLoanConverter;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.config.LoanToLoanResponseConverter;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions.BadParametersException;
+import net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions.EntityInvalidOperationException;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.exceptions.EntityNotFoundException;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api.BookResponse;
 import net.unir.missi.desarrollowebfullstack.bookabook.operador.model.api.ClientResponse;
@@ -19,6 +20,7 @@
 import org.springframework.stereotype.Service;
 
 import java.awt.print.Book;
+import java.time.LocalDate;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
@@ -51,7 +53,7 @@ public class LoanService implements ILoanService {
     // CRUD
 
     @Override
-    public List<LoanResponse> getAllLoans(Long bookId, Long clientId, Date loanDate, Date returnDate, Date dueDate, Boolean isReturned, Integer renewalCount) {
+    public List<LoanResponse> getAllLoans(Long bookId, Long clientId, LocalDate loanDate, LocalDate returnDate, LocalDate dueDate, Boolean isReturned, Integer renewalCount) {
         Loan loan = new Loan(null, bookId, clientId, loanDate, returnDate, dueDate, isReturned, renewalCount);
         List<Loan> loanList;
         if (this.isValidSyntaxLoanForNulls(loan)) {
@@ -75,25 +77,30 @@ public LoanResponse createLoan(LoanRequest request) {
             throw new BadParametersException("One or more parameters of the request are wrong", null);
         }
 
-        Logger.getGlobal().warning("hasta aki");
         // If loan referencing non-existing books throw 404
         if (! isExistingBook(loan.getBookId().toString()))
         {
             throw new EntityNotFoundException("Book id " + loan.getBookId() + " does not exist.", null);
         }
-
-        Logger.getGlobal().warning("hasta aki existe book");
         // If loan referencing non-existing clients throw 404
         if(! isExistingClient(loan.getClientId().toString()))
         {
             throw new EntityNotFoundException("Client id " + loan.getClientId() + " does not exist.", null);
         }
 
-        Logger.getGlobal().warning("hasta aki existe client");
+        List<Loan> foundLoanedBook = loanRepository.findByBookIdAndIsReturned(request.getBookId(), false);
+        Logger.getGlobal().warning("Book Count: " + foundLoanedBook.stream().count());
+
+        if((long) foundLoanedBook.size() != 0) {
+            Logger.getGlobal().warning("Error: Book " + request.getBookId() + " cannot be loaned because it's already loaned to other client");
+            throw new EntityInvalidOperationException("Error: Book " + request.getBookId() + " cannot be loaned because it's already loaned to other client", null);
+        }
+
+        loan.setLoanDate(LocalDate.now());
+        loan.setDueDate(loan.getLoanDate().plusDays(7));
 
         // Implicit else: valid loan is saved in the DB
         Loan createdLoan = loanRepository.save(loan);
-        Logger.getGlobal().warning("hasta aki ya se ha guardao");
         return this.loanToLoanResponseConverter.convert(createdLoan);
     }
 
@@ -151,20 +158,12 @@ public LoanResponse modifyAllLoanData(LoanRequest loanRequest, Long id) {
     }
 
     @Override
-    public LoanResponse modifyLoan(LoanRequest loanRequest, Long id) {
-        Loan loan = this.loanRequestToLoanConverter.convert(loanRequest);
-
+    public LoanResponse modifyLoan(boolean isReturned, Long id) {
         // If loan has null values or wrong values throw 400
-        if (
-                ! this.isValidSyntaxLoanForNulls(Objects.requireNonNull(loan))
-                        || ! this.isValidSyntaxLoanForZeroes(loan))
-        {
-            throw new BadParametersException("One or more parameters of the request are wrong", null);
-        }
 
         // If loan does not exist throw 404
-        Loan loanMatched = loanRepository.findById(id);
-        if (loanMatched == null)
+        Loan loan = loanRepository.findById(id);
+        if (loan == null)
         {
             throw new EntityNotFoundException("Loan with id " + id.toString() + " does not exist", null);
         }
@@ -181,14 +180,20 @@ public LoanResponse modifyLoan(LoanRequest loanRequest, Long id) {
             throw new EntityNotFoundException("Client id " + loan.getClientId() + " does not exist.", null);
         }
 
-        // Update values of matched loan with values of received request
-        Loan mergedLoan = this.loanMergerNonEmpty.merge(loanMatched, loan);
+        if(isReturned) {
+            loan.setReturnDate(LocalDate.now());
+            loan.setIsReturned(true);
+        }
+        else if(!loan.getIsReturned()) {
+            loan.setDueDate(LocalDate.now().plusDays(7));
+            loan.setRenewalCount(loan.getRenewalCount() + 1);
+        }
 
         // Save updated loan
-        mergedLoan = this.loanRepository.save(mergedLoan);
+        this.loanRepository.save(loan);
 
         // Return response
-        return this.loanToLoanResponseConverter.convert(mergedLoan);
+        return this.loanToLoanResponseConverter.convert(loan);
     }
 
     @Override
@@ -222,7 +227,6 @@ public List<LoanResponse> getLoansByClientId(Long clientId) {
     private boolean isExistingBook(String id) {
         try {
             ResponseEntity<BookResponse> book = buscadorClient.getBook(id);
-            Logger.getGlobal().warning("MyText");
             return book != null;
         }
         catch(Exception e) {
@@ -230,10 +234,20 @@ private boolean isExistingBook(String id) {
         }
     }
 
+    private BookResponse getBook(String id) {
+        try {
+            ResponseEntity<BookResponse> book = buscadorClient.getBook(id);
+            BookResponse response = book.getBody();
+            return response;
+        }
+        catch(Exception e) {
+            return null;
+        }
+    }
+
     private boolean isExistingClient(String id) {
         try {
             ResponseEntity<ClientResponse> client = buscadorClient.getClient(id);
-            Logger.getGlobal().warning("MyText");
             return client != null;
         }
         catch(Exception e) {
@@ -243,13 +257,7 @@ private boolean isExistingClient(String id) {
 
     private boolean isValidSyntaxLoanForNulls(Loan loan)
     {
-        return loan.getBookId() != null
-                && loan.getClientId() != null
-                && loan.getLoanDate() != null
-                && loan.getReturnDate() != null
-                && loan.getDueDate() != null
-                && loan.getIsReturned() != null
-                && loan.getRenewalCount() != null;
+        return loan.getBookId() != null && loan.getClientId() != null;
     }
 
     private boolean isValidSyntaxLoanForZeroes(Loan loan)