diff --git a/pom.xml b/pom.xml
index d693ad2..d292734 100755
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>3.5.6</version>
+        <version>3.5.7</version>
         <relativePath/> <!-- lookup parent from repository -->
     </parent>
     <groupId>nl.connected-it</groupId>
@@ -50,10 +50,7 @@
             <artifactId>h2</artifactId>
             <scope>runtime</scope>
         </dependency>
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-security</artifactId>
-        </dependency>
+
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-web</artifactId>
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Event.java b/src/main/java/nl/connectedit/swiss/domain/entity/Event.java
index 34bfeb4..32b5225 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Event.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Event.java
@@ -26,7 +26,7 @@ public class Event extends AbstractEntity {
     @ManyToOne
     private Tournament tournament;
 
-    @OneToMany(cascade = CascadeType.MERGE, fetch = FetchType.LAZY)
+    @OneToMany(mappedBy = "event", cascade = CascadeType.MERGE, fetch = FetchType.LAZY)
     private List<Registration> registrations;
 
     @Enumerated(EnumType.STRING)
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Match.java b/src/main/java/nl/connectedit/swiss/domain/entity/Match.java
index 9c651a7..37ddf3b 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Match.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Match.java
@@ -30,9 +30,11 @@ public class Match extends AbstractEntity {
     private Round round;
 
     @ManyToOne
+    @JoinColumn(name = "team1_id")
     private Team team1;
 
     @ManyToOne
+    @JoinColumn(name = "team2_id")
     private Team team2;
 
     private Boolean played;
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Player.java b/src/main/java/nl/connectedit/swiss/domain/entity/Player.java
index 4c2fca9..8d4f040 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Player.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Player.java
@@ -58,11 +58,11 @@ public class Player extends AbstractEntity {
     @Enumerated(EnumType.STRING)
     private PlayerStrength strength;
 
-    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
-    private List<Registration> registrations;// = new ArrayList<>();
+    @OneToMany(mappedBy = "player", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
+    private List<Registration> registrations;
 
-    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
-    private List<Registration> partnerRegistrations;// = new ArrayList<>();
+    @OneToMany(mappedBy = "partner", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
+    private List<Registration> partnerRegistrations;
 
     public String getFullName() {
         return hasLength(middleName) ?
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Registration.java b/src/main/java/nl/connectedit/swiss/domain/entity/Registration.java
index 9309895..8a67e0e 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Registration.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Registration.java
@@ -20,8 +20,8 @@ public class Registration extends AbstractEntity {
     @ManyToOne
     private Event event;
 
-    @ManyToOne
-    private Tournament tournament;
+//    @ManyToOne
+//    private Tournament tournament;
 
     @ManyToOne
     @JoinColumn(name = "player_id")
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Round.java b/src/main/java/nl/connectedit/swiss/domain/entity/Round.java
index b47a167..f10a3c3 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Round.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Round.java
@@ -27,7 +27,7 @@ public class Round extends AbstractEntity {
 
     private Status status;
 
-    @OneToMany(cascade = CascadeType.MERGE, fetch = FetchType.LAZY)
+    @OneToMany(mappedBy = "round", cascade = CascadeType.MERGE, fetch = FetchType.LAZY)
     @OrderBy("id")
     private List<Match> matches;
 
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Tournament.java b/src/main/java/nl/connectedit/swiss/domain/entity/Tournament.java
index 8e695f3..528e076 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Tournament.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Tournament.java
@@ -35,7 +35,7 @@ public class Tournament extends AbstractEntity {
     @Enumerated(EnumType.STRING)
     private TournamentStatus status;
 
-    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
+    @OneToMany(mappedBy = "tournament", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
     private List<Event> events;
 
     @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
diff --git a/src/main/java/nl/connectedit/swiss/mapper/TournamentMapper.java b/src/main/java/nl/connectedit/swiss/mapper/TournamentMapper.java
index 9e34731..2fb50a2 100644
--- a/src/main/java/nl/connectedit/swiss/mapper/TournamentMapper.java
+++ b/src/main/java/nl/connectedit/swiss/mapper/TournamentMapper.java
@@ -94,13 +94,15 @@ public class TournamentMapper implements DtoMapper<Tournament, TournamentDto>, E
     var playersCounting = new ArrayList<Long>();
 
     for (var event : tournament.getEvents()) {
-      for (var group : event.getGroups()) {
-        for (var round : group.getRounds()) {
-          for (var match : round.getMatches()) {
-            if (match.getStatus() == Status.IN_PROGRESS && match.getCounter() != null) {
-              var counter = getTournamentPlayerFromPlayerId(tournament, match.getCounter().getId());
-              if (counter != null) {
-                playersCounting.add(counter.getId());
+      if (event.getGroups() != null) {
+        for (var group : event.getGroups()) {
+          for (var round : group.getRounds()) {
+            for (var match : round.getMatches()) {
+              if (match.getStatus() == Status.IN_PROGRESS && match.getCounter() != null) {
+                var counter = getTournamentPlayerFromPlayerId(tournament, match.getCounter().getId());
+                if (counter != null) {
+                  playersCounting.add(counter.getId());
+                }
               }
             }
           }
@@ -114,11 +116,13 @@ public class TournamentMapper implements DtoMapper<Tournament, TournamentDto>, E
     var playersPlaying = new ArrayList<Long>();
 
     for (var event : tournament.getEvents()) {
-      for (var group : event.getGroups()) {
-        for (var round : group.getRounds()) {
-          for (var match : round.getMatches()) {
-            if (match.getStatus() == Status.IN_PROGRESS) {
-              playersPlaying.addAll(getPlayersInMatch(tournament, match));
+      if (event.getGroups() != null) {
+        for (var group : event.getGroups()) {
+          for (var round : group.getRounds()) {
+            for (var match : round.getMatches()) {
+              if (match.getStatus() == Status.IN_PROGRESS) {
+                playersPlaying.addAll(getPlayersInMatch(tournament, match));
+              }
             }
           }
         }
@@ -129,6 +133,10 @@ public class TournamentMapper implements DtoMapper<Tournament, TournamentDto>, E
   }
 
   private List<Long> getPlayersAvailable(Tournament tournament) {
+    if (tournament.getTournamentPlayers() == null) {
+      return List.of();
+    }
+
     var playersAvailable = tournament.getTournamentPlayers()
       .stream()
       .map(TournamentPlayer::getId)
diff --git a/src/main/java/nl/connectedit/swiss/service/RegistrationService.java b/src/main/java/nl/connectedit/swiss/service/RegistrationService.java
index a7aed17..761eeb7 100644
--- a/src/main/java/nl/connectedit/swiss/service/RegistrationService.java
+++ b/src/main/java/nl/connectedit/swiss/service/RegistrationService.java
@@ -27,7 +27,7 @@ public class RegistrationService {
         .findAny();
       if (optionalExistingPlayerRegistration.isEmpty()) { // no previous registration for this event
         var newRegistration = new Registration();
-        newRegistration.setTournament(tournament);
+//        newRegistration.setTournament(tournament);
         newRegistration.setEvent(event);
         newRegistration.setPlayer(player);
         if (eventRegistration.getPartner() != null) {