Currency not getting added between levels

Hello, I want the Currency collected during a level of my game to be added afterwards. But instead this is happening:

1st Run: Player collects 2 Coins during Run -> 2 Coins is being shown in the Main Menu

2nd Run: Player collects 0 coins during Run -> 0 Coins is being shown in the Main Menu

I'm trying to fix this bug since days and rewrote my code several times. I would appreciate any help!

The code for the Main Menu:

 public class MainMenuManager : MonoBehaviour {
 
     public int HighScore=0;
     public int reachedScore;
     public Text HighScoreUI;
     public Text CurrencyUI;
 
     public int currency;
 
 
     // Use this for initialization
     void Start () {
   
        
         HighScore = PlayerPrefs.GetInt("HighScore");
         currency = PlayerPrefs.GetInt("Currency");
 
       
     }
     
     // Update is called once per frame
     void Update () {
 
         CurrencyUI.text = " " + currency.ToString("0");
         HighScoreUI.text = "High Score: " + HighScore;
         PlayerPrefs.SetInt("Currency", currency);
         
     }
 }

Code for collecting the currency:

 void OnTriggerEnter2D(Collider2D other)
 {
 
    if(other.gameObject.tag=="Currency" && playerDead == false)
         {
             gameManager.currency += 1; //Currency is being added to the GameManager
             barking.Play();
             Destroy(other.gameObject);
         }
 
 
 
 }

And the Code for the GameManager:

 public class Gamemanager : MonoBehaviour {
 
  public  int currency; //being accessed by the GameObject onTriggerEnter
         private string activeScene;
         private int balance;
     
     
         void Start () {
     
             gameOverObjects = GameObject.FindGameObjectsWithTag("ShowOnGameOver");
     
             for(int i=0; i<gameOverObjects.Length;i++)
             {
                 gameOverObjects[i].SetActive(false);
             }
     
             render = player.GetComponent<SpriteRenderer>();
     
             playeranim = player.GetComponent<Animator>();
     
             defeatMusic = gameObject.GetComponent<AudioSource>();
     
             balance = PlayerPrefs.GetInt("Currency"); //PlayerPrefs is set in MainMenu
     
             activeScene = PlayerPrefs.GetString("Scene");
         }
         
         // Update is called once per frame
         void Update () {
             score += PointsPerSecond * Time.deltaTime;
             scoreUI.text = "Score: " + score.ToString("0");
             currencyUI.text = ": " + currency.ToString("0");
     
         }
     
         public void restartGame()
         {
             StartCoroutine("RestartGameCo");
         }
     
         public IEnumerator RestartGameCo()
         {
             yield return new WaitForSeconds(0.5f);
             PlayerPrefs.SetInt("Player Score", (int)score);
     
             PlayerPrefs.SetInt("Currency", balance+currency); //Collected currency is added to the balance and saved to the PlayerPref
             playeranim.SetBool("gameover", true);
             activeScene = PlayerPrefs.GetString("Scene");
             if (activeScene == "ben")
             {
                 Application.LoadLevel("gameOver2");
             }
     
             if(activeScene == "ben_desert")
             {
                 Application.LoadLevel("gameOverDesert");
             }
     
             if(activeScene == "ben_winter")
             {
                 Application.LoadLevel("gameOverWinter");
             }
             
            
     
             for (int i = 0; i < gameOverObjects.Length; i++)
             {
                 gameOverObjects[i].SetActive(true);
             }
     

         }
     
 }