diff --git a/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameEntity.java b/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameEntity.java
index 4f22c9d..c9f57d7 100644
--- a/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameEntity.java
+++ b/backend/src/main/java/de/szut/casino/blackjack/BlackJackGameEntity.java
@@ -4,6 +4,8 @@ import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonManagedReference;
 import de.szut.casino.user.UserEntity;
 import jakarta.persistence.*;
+import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.Positive;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
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 cbdbc27..272334d 100644
--- a/backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java
+++ b/backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java
@@ -11,28 +11,27 @@ import org.springframework.stereotype.Service;
 
 import java.math.BigDecimal;
 import java.util.List;
-import java.util.Random;
 
 @Service
 public class BlackJackService {
     private final BlackJackGameRepository blackJackGameRepository;
     private final UserRepository userRepository;
-    private final Random random;
     private final BalanceService balanceService;
     private final UserService userService;
+    private final DeckService deckService;
 
     public BlackJackService(
             BlackJackGameRepository blackJackGameRepository,
             UserRepository userRepository,
-            Random random,
             BalanceService balanceService,
-            UserService userService
+            UserService userService,
+            DeckService deckService
     ) {
         this.blackJackGameRepository = blackJackGameRepository;
         this.userRepository = userRepository;
-        this.random = random;
         this.balanceService = balanceService;
         this.userService = userService;
+        this.deckService = deckService;
     }
 
     public BlackJackGameEntity getBlackJackGame(Long id) {
@@ -53,8 +52,8 @@ public class BlackJackService {
         game.setUser(user);
         game.setBet(betDto.getBetAmount());
 
-        initializeDeck(game);
-        dealInitialCards(game);
+        this.deckService.initializeDeck(game);
+        this.deckService.dealInitialCards(game);
 
         game.setState(getState(game));
 
@@ -67,7 +66,7 @@ public class BlackJackService {
             return game;
         }
 
-        dealCardToPlayer(game);
+        this.deckService.dealCardToPlayer(game);
         updateGameStateAndBalance(game);
 
         return processGameBasedOnState(game);
@@ -91,14 +90,14 @@ public class BlackJackService {
             return game;
         }
 
-        UserEntity user = getUserWithFreshData(game.getUser());
+        UserEntity user = game.getUser();
         BigDecimal additionalBet = game.getBet();
 
         this.balanceService.subtractFunds(user, additionalBet);
 
         game.setBet(game.getBet().add(additionalBet));
 
-        dealCardToPlayer(game);
+        this.deckService.dealCardToPlayer(game);
         updateGameStateAndBalance(game);
 
         if (game.getState() == BlackJackState.IN_PROGRESS) {
@@ -117,36 +116,6 @@ public class BlackJackService {
         return blackJackGameRepository.save(game);
     }
 
-    private UserEntity getUserWithFreshData(UserEntity user) {
-        return userRepository.findById(user.getId()).orElse(user);
-    }
-
-    private void dealInitialCards(BlackJackGameEntity game) {
-        for (int i = 0; i < 2; i++) {
-            dealCardToPlayer(game);
-        }
-
-        dealCardToDealer(game);
-    }
-
-    private void dealCardToPlayer(BlackJackGameEntity game) {
-        CardEntity card = drawCardFromDeck(game);
-        card.setCardType(CardType.PLAYER);
-        game.getPlayerCards().add(card);
-    }
-
-    private void dealCardToDealer(BlackJackGameEntity game) {
-        CardEntity card = drawCardFromDeck(game);
-        card.setCardType(CardType.DEALER);
-        game.getDealerCards().add(card);
-    }
-
-    private void dealCardsToDealerUntilMinimumScore(BlackJackGameEntity game) {
-        while (calculateHandValue(game.getDealerCards()) < 17) {
-            dealCardToDealer(game);
-        }
-    }
-
     private void updateGameStateAndBalance(BlackJackGameEntity game) {
         game.setState(getState(game));
 
@@ -174,7 +143,7 @@ public class BlackJackService {
     }
 
     protected void updateUserBalance(BlackJackGameEntity game, boolean isWin) {
-        UserEntity user = getUserWithFreshData(game.getUser());
+        UserEntity user = game.getUser();
         BigDecimal totalBet = game.getBet();
         BigDecimal balance = user.getBalance();
 
@@ -188,34 +157,11 @@ public class BlackJackService {
         userRepository.save(user);
     }
 
-    private void initializeDeck(BlackJackGameEntity game) {
-        for (Suit suit : Suit.values()) {
-            for (Rank rank : Rank.values()) {
-                CardEntity card = new CardEntity();
-                card.setGame(game);
-                card.setSuit(suit);
-                card.setRank(rank);
-                card.setCardType(CardType.DECK);
-                game.getDeck().add(card);
-            }
-        }
-
-        java.util.Collections.shuffle(game.getDeck(), random);
-    }
-
-    private CardEntity drawCardFromDeck(BlackJackGameEntity game) {
-        if (game.getDeck().isEmpty()) {
-            throw new IllegalStateException("Deck is empty");
-        }
-
-        return game.getDeck().removeFirst();
-    }
-
     private BlackJackState getState(BlackJackGameEntity game) {
         int playerHandValue = calculateHandValue(game.getPlayerCards());
 
         if (playerHandValue == 21) {
-            CardEntity hole = drawCardFromDeck(game);
+            CardEntity hole = this.deckService.drawCardFromDeck(game);
             hole.setCardType(CardType.DEALER);
             game.getDealerCards().add(hole);
 
@@ -225,7 +171,7 @@ public class BlackJackService {
                 return BlackJackState.DRAW;
             } else {
                 BigDecimal blackjackWinnings = game.getBet().multiply(new BigDecimal("1.5"));
-                UserEntity user = getUserWithFreshData(game.getUser());
+                UserEntity user = game.getUser();
                 user.setBalance(user.getBalance().add(blackjackWinnings));
                 return BlackJackState.PLAYER_BLACKJACK;
             }
@@ -253,4 +199,12 @@ public class BlackJackService {
 
         return sum;
     }
+
+    private void dealCardsToDealerUntilMinimumScore(BlackJackGameEntity game) {
+        while (calculateHandValue(game.getDealerCards()) < 17) {
+            this.deckService.dealCardToDealer(game);
+        }
+    }
 }
+
+
diff --git a/backend/src/main/java/de/szut/casino/blackjack/DeckService.java b/backend/src/main/java/de/szut/casino/blackjack/DeckService.java
new file mode 100644
index 0000000..0511abd
--- /dev/null
+++ b/backend/src/main/java/de/szut/casino/blackjack/DeckService.java
@@ -0,0 +1,57 @@
+package de.szut.casino.blackjack;
+
+import org.springframework.stereotype.Service;
+
+import java.util.Random;
+
+@Service
+public class DeckService {
+    private final Random random;
+
+    public DeckService(Random random) {
+        this.random = random;
+    }
+
+    public void initializeDeck(BlackJackGameEntity game) {
+        for (Suit suit : Suit.values()) {
+            for (Rank rank : Rank.values()) {
+                CardEntity card = new CardEntity();
+                card.setGame(game);
+                card.setSuit(suit);
+                card.setRank(rank);
+                card.setCardType(CardType.DECK);
+                game.getDeck().add(card);
+            }
+        }
+
+        java.util.Collections.shuffle(game.getDeck(), random);
+    }
+
+    public CardEntity drawCardFromDeck(BlackJackGameEntity game) {
+        if (game.getDeck().isEmpty()) {
+            throw new IllegalStateException("Deck is empty");
+        }
+
+        return game.getDeck().removeFirst();
+    }
+
+    public void dealInitialCards(BlackJackGameEntity game) {
+        for (int i = 0; i < 2; i++) {
+            dealCardToPlayer(game);
+        }
+
+        dealCardToDealer(game);
+    }
+
+    public void dealCardToPlayer(BlackJackGameEntity game) {
+        CardEntity card = drawCardFromDeck(game);
+        card.setCardType(CardType.PLAYER);
+        game.getPlayerCards().add(card);
+    }
+
+    public void dealCardToDealer(BlackJackGameEntity game) {
+        CardEntity card = drawCardFromDeck(game);
+        card.setCardType(CardType.DEALER);
+        game.getDealerCards().add(card);
+    }
+}
diff --git a/backend/src/main/java/de/szut/casino/user/UserEntity.java b/backend/src/main/java/de/szut/casino/user/UserEntity.java
index c263d9c..534859f 100644
--- a/backend/src/main/java/de/szut/casino/user/UserEntity.java
+++ b/backend/src/main/java/de/szut/casino/user/UserEntity.java
@@ -16,6 +16,9 @@ public class UserEntity {
     @GeneratedValue
     private Long id;
 
+    @Version
+    private Long version;
+
     @Column(unique = true)
     private String email;
 
@@ -44,7 +47,6 @@ public class UserEntity {
         this.password = password;
         this.balance = balance;
         this.verificationToken = verificationToken;
-        this.provider = AuthProvider.LOCAL;
     }
 
     public UserEntity(String email, String username, AuthProvider provider, String providerId, BigDecimal balance) {