diff --git a/src/include/Activities/FightActivity.hpp b/src/include/Activities/FightActivity.hpp
index 1b795bf..970b074 100644
--- a/src/include/Activities/FightActivity.hpp
+++ b/src/include/Activities/FightActivity.hpp
@@ -40,6 +40,9 @@ class FightActivity: public Activity {
     void runCurrentState(Game &game);
 
   private:
+    /*
+     * fightEnv is a personal current view state of FightActivity. Therefore, can not be included in Game.hpp or a derived class
+    */
     FightEnv fightEnv;
     FightStateEnum currentFightStateEnum = FightStateEnum::TURN_CHANGE;
     std::shared_ptr<Enemy> enemy;
diff --git a/src/include/Game.hpp b/src/include/Game.hpp
index 4be9f14..82bdfcf 100644
--- a/src/include/Game.hpp
+++ b/src/include/Game.hpp
@@ -21,7 +21,7 @@ class Game {
     GameStatus gameStatus;
     sf::RenderWindow& gameWindow;
 
-    Player player = Player("Ipagaxi", 100, 12, {100, 100, 100}, "default_actor_quer.png");
+    std::shared_ptr<Player> player = std::make_shared<Player>(Player("Ipagaxi", 100, 12, {100, 100, 100}, "default_actor_quer.png"));
 
     static Game& getInstance();
 
diff --git a/src/include/GameStatus.hpp b/src/include/GameStatus.hpp
index d707b34..b777365 100644
--- a/src/include/GameStatus.hpp
+++ b/src/include/GameStatus.hpp
@@ -3,6 +3,7 @@
 
 #include <SFML/Graphics.hpp>
 
+
 class GameStatus {
   public:
     sf::Time elapsedTime;
diff --git a/src/include/ObserverPattern/Observer.hpp b/src/include/ObserverPattern/Observer.hpp
index 125739a..db05a8b 100644
--- a/src/include/ObserverPattern/Observer.hpp
+++ b/src/include/ObserverPattern/Observer.hpp
@@ -12,20 +12,25 @@ class Observer {
     //Observer(Actor& subject);
     virtual ~Observer();
     virtual void onNotify(int newValue);
+    void invalidateSubject();
+
   private:
-    Subject* subject;
+  Subject* subject;
 };
 
 class Subject {
   public:
-  void attachObserver(Observer& observer);
-  void detachObserver(Observer& observer);
+    ~Subject();
+    using RefObserver = std::reference_wrapper<Observer>;
+    void attachObserver(Observer& observer);
+    void detachObserver(Observer& observer);
+    bool valid = true;
 
   private:
-  std::list<Observer> observers;
+    std::list<RefObserver> observers;
 
   protected:
-  virtual void notify(int newValue);
+    virtual void notify(int newValue);
 };
 
 #endif
\ No newline at end of file
diff --git a/src/include/UIElements/UIStats.hpp b/src/include/UIElements/UIStats.hpp
index 0cc893d..324b011 100644
--- a/src/include/UIElements/UIStats.hpp
+++ b/src/include/UIElements/UIStats.hpp
@@ -12,7 +12,7 @@
 class UIStats: public UIElement, Observer {
   public:
     ~UIStats();
-    UIStats(Actor& actor);
+    UIStats(std::shared_ptr<Actor> actor);
     void init(Actor actor);
     void draw() override;
     sf::Vector2f getPosition() override;
diff --git a/src/include/UIObjects/UIEnemyOverview.hpp b/src/include/UIObjects/UIEnemyOverview.hpp
index 3c745c6..3f1eb13 100644
--- a/src/include/UIObjects/UIEnemyOverview.hpp
+++ b/src/include/UIObjects/UIEnemyOverview.hpp
@@ -13,7 +13,7 @@
 
 class UIEnemyOverview {
   public:
-    UIEnemyOverview(Enemy& enemy);
+    UIEnemyOverview(std::shared_ptr<Enemy> enemy);
     Enemy enemy;
     UIColorPicker colorPicker = UIColorPicker("colorPIC_default.png", "color_picker_border.png");
     sf::Text pickedColorText;
diff --git a/src/main/Activities/FightActivity.cpp b/src/main/Activities/FightActivity.cpp
index fc72638..e10b386 100644
--- a/src/main/Activities/FightActivity.cpp
+++ b/src/main/Activities/FightActivity.cpp
@@ -4,7 +4,7 @@
 FightActivity::FightActivity() : Activity(), fightEnv(), currentFightState(std::make_unique<TurnChangeState>(fightEnv)) {
   Game& game = Game::getInstance();
   this->enemy = std::make_shared<Enemy>(this->initEnemy());
-  this->fightEnv.enemyOverview = std::make_unique<UIEnemyOverview>(*this->enemy);
+  this->fightEnv.enemyOverview = std::make_unique<UIEnemyOverview>(this->enemy);
   this->fightEnv.playerOverview.init();
 
   this->fightEnv.backgroundTX.loadFromFile(RESOURCE_PATH "backgrounds/background_fight.png");
@@ -42,7 +42,6 @@ FightActivity::FightActivity() : Activity(), fightEnv(), currentFightState(std::
 }
 
 FightActivity::~FightActivity() {
-  //delete this->fightEnv.enemyOverview;
   this->fightEnv.backgroundMusic.stop();
 }
 
diff --git a/src/main/FightStates/PlayersTurn.cpp b/src/main/FightStates/PlayersTurn.cpp
index 71ba6a6..a514892 100644
--- a/src/main/FightStates/PlayersTurn.cpp
+++ b/src/main/FightStates/PlayersTurn.cpp
@@ -20,7 +20,7 @@ FightStateEnum PlayersTurn::run(FightEnv &fightEnv) {
         fightEnv.pickedColor = fightEnv.enemyOverview->colorPicker.getPixelColor(clickedPos);
         fightEnv.enemyOverview->updatePickedColorText("(" + std::to_string(fightEnv.pickedColor.r) +  ", " + std::to_string(fightEnv.pickedColor.g) + ", " + std::to_string(fightEnv.pickedColor.b) + ")", fightEnv.pickedColor);
         float attackMultiplier = this->calculateAttackMult(fightEnv);
-        int damage = game.player.attackStrength * attackMultiplier;
+        int damage = game.player->attackStrength * attackMultiplier;
         int millSecToLive = 600;
         fightEnv.textFadingManager.startAnimation(std::to_string(damage), clickedPos, sf::Color::Yellow, game.gameWindow.getSize().y * 0.05, AnimationPath::Parabel, millSecToLive);
         fightEnv.enemyOverview->changeHealth(damage);
diff --git a/src/main/ObserverPattern/Observer.cpp b/src/main/ObserverPattern/Observer.cpp
index 134555b..2c6bc9d 100644
--- a/src/main/ObserverPattern/Observer.cpp
+++ b/src/main/ObserverPattern/Observer.cpp
@@ -8,11 +8,25 @@ Observer::Observer() {
 
 Observer::~Observer() {
   std::cout << "~Observer" << std::endl;
-  this->subject->detachObserver(*this);
+  if (subject && subject->valid) {
+    subject->detachObserver(*this);
+  }
 }
 
 void Observer::onNotify(int newValue) {}
 
+void Observer::invalidateSubject() {
+  this->subject = nullptr;
+}
+
+Subject::~Subject() {
+  this->valid = false;
+  for (RefObserver& obs : observers) {
+    obs.get().invalidateSubject();
+  }
+}
+
+
 void Subject::notify(int newValue) {
   for (Observer obs: observers) {
     obs.onNotify(newValue);
@@ -20,13 +34,13 @@ void Subject::notify(int newValue) {
 }
 
 void Subject::attachObserver(Observer &observer) {
-  std::cout << "Observer attached" << std::endl;
   this->observers.push_front(observer);
 }
 
 void Subject::detachObserver(Observer &observer) {
   std::cout << "Size: " << this->observers.size() << std::endl;
-  this->observers.remove_if([&observer] (const Observer obs) {
-    return &obs == &observer;
+  this->observers.remove_if([&observer] (const RefObserver& obs) {
+
+    return &obs.get() == &observer;
   });
 }
\ No newline at end of file
diff --git a/src/main/UIElements/UIStats.cpp b/src/main/UIElements/UIStats.cpp
index 4a8a688..78c886f 100644
--- a/src/main/UIElements/UIStats.cpp
+++ b/src/main/UIElements/UIStats.cpp
@@ -4,9 +4,9 @@ UIStats::~UIStats() {
   std::cout << "~UIStats" << std::endl;
 }
 
-UIStats::UIStats(Actor& actor) {
+UIStats::UIStats(std::shared_ptr<Actor> actor) {
   std::cout << "UIStats(actor)" << std::endl;
-  actor.attachObserver(*this);
+  actor->attachObserver(*this);
   Game& game = Game::getInstance();
   sf::Vector2u windowSize = game.gameWindow.getSize();
   sf::Color statsValueFontColor = sf::Color::Yellow;
@@ -20,7 +20,7 @@ UIStats::UIStats(Actor& actor) {
   this->actorStatsBox.setBackgroundMargin(actorStatsBoxSize.width * 0.1, actorStatsBoxSize.height * 0.04);
 
   this->actorName.setFont(game.mainFont);
-  this->actorName.setString(actor.name);
+  this->actorName.setString(actor->name);
   this->actorName.setCharacterSize(windowSize.y*0.02);
   this->actorName.setFillColor(sf::Color::White);
 
@@ -30,7 +30,7 @@ UIStats::UIStats(Actor& actor) {
   this->actorHealthLabel.setFillColor(statsLabelFontColor);
 
   this->actorHealthValue.setFont(game.mainFont);
-  this->actorHealthValue.setString(std::to_string(actor.health));
+  this->actorHealthValue.setString(std::to_string(actor->health));
   this->actorHealthValue.setCharacterSize(statsTextHeight);
   this->actorHealthValue.setFillColor(statsValueFontColor);
 
@@ -40,7 +40,7 @@ UIStats::UIStats(Actor& actor) {
   this->actorAttackStrengthLabel.setFillColor(statsLabelFontColor);
 
   this->actorAttackStrengthValue.setFont(game.mainFont);
-  this->actorAttackStrengthValue.setString(std::to_string(actor.attackStrength));
+  this->actorAttackStrengthValue.setString(std::to_string(actor->attackStrength));
   this->actorAttackStrengthValue.setCharacterSize(statsTextHeight);
   this->actorAttackStrengthValue.setFillColor(statsValueFontColor);
 
@@ -50,7 +50,7 @@ UIStats::UIStats(Actor& actor) {
   this->actorRGBDefenseLabel.setFillColor(statsLabelFontColor);
 
   this->actorRGBDefenseValues.setFont(game.mainFont);
-  this->actorRGBDefenseValues.setString("(" + std::to_string(actor.defense.red) + ", " + std::to_string(actor.defense.green) + ", " + std::to_string(actor.defense.blue) + ")");
+  this->actorRGBDefenseValues.setString("(" + std::to_string(actor->defense.red) + ", " + std::to_string(actor->defense.green) + ", " + std::to_string(actor->defense.blue) + ")");
   this->actorRGBDefenseValues.setCharacterSize(statsTextHeight);
   this->actorRGBDefenseValues.setFillColor(statsValueFontColor);
 
diff --git a/src/main/UIObjects/UIEnemyOverview.cpp b/src/main/UIObjects/UIEnemyOverview.cpp
index f86a6b3..6be6f72 100644
--- a/src/main/UIObjects/UIEnemyOverview.cpp
+++ b/src/main/UIObjects/UIEnemyOverview.cpp
@@ -1,10 +1,8 @@
 #include "UIObjects/UIEnemyOverview.hpp"
 
-UIEnemyOverview::UIEnemyOverview(Enemy &_enemy): enemyBorderedImage("monster_landscape_cut/" + _enemy.picPath, "actor_borders/fight_border.png"), enemyStats(_enemy) {
+UIEnemyOverview::UIEnemyOverview(std::shared_ptr<Enemy> _enemy): enemyBorderedImage("monster_landscape_cut/" + (*_enemy).picPath, "actor_borders/fight_border.png"), enemyStats(_enemy) {
   Game& game = Game::getInstance();
-  this->enemy = _enemy;
-  //this->enemyBorderedImage.init("monster_landscape_cut/" + enemy.picPath, "actor_borders/fight_border.png");
-  //this->enemyStats.init(_enemy);
+  this->enemy = *_enemy;
 
   sf::Vector2u windowSize = game.gameWindow.getSize();
   sf::FloatRect boxRect = this->box.getSize();
diff --git a/src/main/UIObjects/UIPlayerOverview.cpp b/src/main/UIObjects/UIPlayerOverview.cpp
index 9ebdc5a..c0f11fd 100644
--- a/src/main/UIObjects/UIPlayerOverview.cpp
+++ b/src/main/UIObjects/UIPlayerOverview.cpp
@@ -1,6 +1,6 @@
 #include "UIObjects/UIPlayerOverview.hpp"
 
-UIPlayerOverview::UIPlayerOverview(): uiPlayerStats(Game::getInstance().player), playerFrame("monster_landscape_cut/" + Game::getInstance().player.picPath, "actor_borders/fight_border.png") {
+UIPlayerOverview::UIPlayerOverview(): uiPlayerStats(Game::getInstance().player), playerFrame("monster_landscape_cut/" + Game::getInstance().player->picPath, "actor_borders/fight_border.png") {
 
 }