diff --git a/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameController.java b/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameController.java
index d4c0e6e..c780ca9 100644
--- a/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameController.java
+++ b/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameController.java
@@ -1,6 +1,7 @@
 package de.szut.casino.blackjack;
 
 import de.szut.casino.exceptionHandling.exceptions.InsufficientFundsException;
+import de.szut.casino.exceptionHandling.exceptions.UserBlackJackGameMismatchException;
 import de.szut.casino.exceptionHandling.exceptions.UserNotFoundException;
 import de.szut.casino.shared.dto.BetDto;
 import de.szut.casino.shared.service.BalanceService;
@@ -30,85 +31,35 @@ public class BlackJackGameController {
 
     @GetMapping("/blackjack/{id}")
     public ResponseEntity<Object> getGame(@PathVariable Long id) {
-        Optional<UserEntity> optionalUser = userService.getCurrentUser();
-
-        if (optionalUser.isEmpty()) {
-            throw new UserNotFoundException();
-        }
-
-        UserEntity user = optionalUser.get();
-        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
-        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
-            return ResponseEntity.notFound().build();
-        }
+        BlackJackGameEntity game = getBlackJackGame(id);
 
         return ResponseEntity.ok(game);
     }
 
     @PostMapping("/blackjack/{id}/hit")
     public ResponseEntity<Object> hit(@PathVariable Long id) {
-        Optional<UserEntity> optionalUser = userService.getCurrentUser();
-
-        if (optionalUser.isEmpty()) {
-            throw new UserNotFoundException();
-        }
-
-        UserEntity user = optionalUser.get();
-        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
-        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
-            return ResponseEntity.notFound().build();
-        }
+        BlackJackGameEntity game = getBlackJackGame(id);
 
         return ResponseEntity.ok(blackJackService.hit(game));
     }
 
     @PostMapping("/blackjack/{id}/stand")
     public ResponseEntity<Object> stand(@PathVariable Long id) {
-        Optional<UserEntity> optionalUser = userService.getCurrentUser();
-
-        if (optionalUser.isEmpty()) {
-            throw new UserNotFoundException();
-        }
-
-        UserEntity user = optionalUser.get();
-        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
-        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
-            return ResponseEntity.notFound().build();
-        }
+        BlackJackGameEntity game = getBlackJackGame(id);
 
         return ResponseEntity.ok(blackJackService.stand(game));
     }
 
     @PostMapping("/blackjack/{id}/doubleDown")
     public ResponseEntity<Object> doubleDown(@PathVariable Long id) {
-        Optional<UserEntity> optionalUser = userService.getCurrentUser();
-
-        if (optionalUser.isEmpty()) {
-            throw new UserNotFoundException();
-        }
-
-        UserEntity user = optionalUser.get();
-        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
-        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
-            return ResponseEntity.notFound().build();
-        }
+        BlackJackGameEntity game = getBlackJackGame(id);
 
         return ResponseEntity.ok(blackJackService.doubleDown(game));
     }
 
     @PostMapping("/blackjack/{id}/split")
     public ResponseEntity<Object> split(@PathVariable Long id) {
-        Optional<UserEntity> optionalUser = userService.getCurrentUser();
-
-        if (optionalUser.isEmpty()) {
-            throw new UserNotFoundException();
-        }
-
-        UserEntity user = optionalUser.get();
-        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
-        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
-            return ResponseEntity.notFound().build();
-        }
+        BlackJackGameEntity game = getBlackJackGame(id);
 
         return ResponseEntity.ok(blackJackService.split(game));
     }
@@ -129,4 +80,20 @@ public class BlackJackGameController {
 
         return ResponseEntity.ok(blackJackService.createBlackJackGame(user, betDto.getBetAmount()));
     }
+
+    private BlackJackGameEntity getBlackJackGame(Long gameId) {
+        Optional<UserEntity> optionalUser = userService.getCurrentUser();
+
+        if (optionalUser.isEmpty()) {
+            throw new UserNotFoundException();
+        }
+
+        UserEntity user = optionalUser.get();
+        BlackJackGameEntity game = blackJackService.getBlackJackGame(gameId);
+        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
+            throw new UserBlackJackGameMismatchException(gameId);
+        }
+
+        return game;
+    }
 }
diff --git a/backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java b/backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java
index f791d19..5e54efe 100644
--- a/backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java
+++ b/backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java
@@ -124,10 +124,6 @@ public class BlackJackService {
         return blackJackGameRepository.save(game);
     }
 
-    private BlackJackGameEntity refreshGameState(BlackJackGameEntity game) {
-        return blackJackGameRepository.findById(game.getId()).orElse(game);
-    }
-
     private UserEntity getUserWithFreshData(UserEntity user) {
         return userRepository.findById(user.getId()).orElse(user);
     }
@@ -210,7 +206,7 @@ public class BlackJackService {
     }
 
     @Transactional
-    private void updateUserBalance(BlackJackGameEntity game, boolean isWin) {
+    protected void updateUserBalance(BlackJackGameEntity game, boolean isWin) {
         UserEntity user = getUserWithFreshData(game.getUser());
         BigDecimal totalBet = game.getBet();
         BigDecimal balance = user.getBalance();
diff --git a/backend/src/main/java/de/szut/casino/exceptionHandling/GlobalExceptionHandler.java b/backend/src/main/java/de/szut/casino/exceptionHandling/GlobalExceptionHandler.java
index 9c185a8..f07c03a 100644
--- a/backend/src/main/java/de/szut/casino/exceptionHandling/GlobalExceptionHandler.java
+++ b/backend/src/main/java/de/szut/casino/exceptionHandling/GlobalExceptionHandler.java
@@ -2,6 +2,7 @@ package de.szut.casino.exceptionHandling;
 
 import de.szut.casino.exceptionHandling.exceptions.EmailNotVerifiedException;
 import de.szut.casino.exceptionHandling.exceptions.InsufficientFundsException;
+import de.szut.casino.exceptionHandling.exceptions.UserBlackJackGameMismatchException;
 import de.szut.casino.exceptionHandling.exceptions.UserNotFoundException;
 import jakarta.persistence.EntityExistsException;
 import org.springframework.http.HttpStatus;
@@ -38,4 +39,10 @@ public class GlobalExceptionHandler {
         ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), request.getDescription(false));
         return new ResponseEntity<>(errorDetails, HttpStatus.UNAUTHORIZED);
     }
+
+    @ExceptionHandler(UserBlackJackGameMismatchException.class)
+    public ResponseEntity<?> handleUserBlackJackGameMismatchException(UserBlackJackGameMismatchException ex, WebRequest request) {
+        ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), request.getDescription(false));
+        return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
+    }
 }
diff --git a/backend/src/main/java/de/szut/casino/exceptionHandling/exceptions/UserBlackJackGameMismatchException.java b/backend/src/main/java/de/szut/casino/exceptionHandling/exceptions/UserBlackJackGameMismatchException.java
new file mode 100644
index 0000000..22a93cc
--- /dev/null
+++ b/backend/src/main/java/de/szut/casino/exceptionHandling/exceptions/UserBlackJackGameMismatchException.java
@@ -0,0 +1,7 @@
+package de.szut.casino.exceptionHandling.exceptions;
+
+public class UserBlackJackGameMismatchException extends RuntimeException {
+    public UserBlackJackGameMismatchException(Long gameId) {
+        super(String.format("Blackjack game with ID %d not found or does not belong to the current user.", gameId));
+    }
+}