PlayerPrefs not working on android

Hey, I managed to add a score and a highscore counter to my android app. Everything went fine and worked good in Unity. I build my app and wanted to test it on my phone but the highscore counter, which is saved using PlayerPrefs wont show... There are many ways out there but nothing worked :( any ideas ?

Here is my code

 public class Score : MonoBehaviour {
     public Transform Charakter;
     public Text scoreText;
     public Text HighscoreText;
 
     public void Start()
     {
         HighscoreText.text = PlayerPrefs.GetString("HighScore");
         PlayerPrefs.Save();
     }
 
     private void Update()
     {
         scoreText.text = Charakter.position.x.ToString("0");
 
         int score = int.Parse(scoreText.text);
         int highscore = int.Parse(PlayerPrefs.GetString("HighScore"));
 
         if (score > highscore)
         {
             PlayerPrefs.SetString("HighScore", scoreText.text);
             PlayerPrefs.Save();
         }
     }
 }