How To Add PlayerPrefs Scores?

Hello again. This might be a simple question, but how can I add a saved score from one scene to another? So like let's say I have a score of 300, and I do something to load a different scene, played it, got 200 more points, headed back to the first scene and now the score is 500(300 + 200 = 500). How would I add those 200 points to the 300 score? Think of it as a bonus/special stage adding on to your regular score. Please I hope you can help me. My scoring script for scene1 that's attached to the Player:

 public class ScoringScript : MonoBehaviour {
     
     float playerScore = 0;
     public float guiPlacementY1;
     public float guiPlacementX1;
     Stage1 player;
     
     void Start()
     {
         player = GetComponent<Stage1>();
     }
     
     
     public void IncreaseScore(int amount)
     {
         playerScore += amount;
     }
     
     public void DecreaseScore(int amount)
     {
         playerScore -= amount;
     }
     
     
     void OnDisable()
     {
         PlayerPrefs.SetInt ("Score", (int)(playerScore * 5));
         PlayerPrefs.SetString("PlayerName", "High Score");
         PlayerPrefs.Save ();
         Debug.Log("Saved");
     }
     
     void OnGUI()
     {
         
         GUI.Label (new Rect(Screen.width * guiPlacementX1, Screen.height * guiPlacementY1, Screen.width * .5f, Screen.height * .4f), "Score: " + (int)(playerScore * 5));
     }
 }

And the script that displays the score:

 public class GameOver : MonoBehaviour {
 
     int score = 0;
     int highscore = 0;
 
     public float guiPlacementY1;
     public float guiPlacementY2;
 
     public float guiPlacementX1;
     public float guiPlacementX2;
     
 
 
     void Start () {
                 score = PlayerPrefs.GetInt ("Score");
                 highscore = PlayerPrefs.GetInt ("High Score");
                 Debug.Log ("M");
                 if (score > highscore) { //when player dies set highscore = to that score
                         highscore = score;
                         PlayerPrefs.SetInt ("High Score", highscore);
                         Debug.Log("ik");
                     
         }
     }
 
         
     void OnGUI()
     {
 
         GUI.Label (new Rect (Screen.width * guiPlacementX1, Screen.height * guiPlacementY1, Screen.width * .5f, Screen.height * .4f), "GAME OVER");
         
         GUI.Label (new Rect (Screen.width * guiPlacementX2, Screen.height * guiPlacementY2, Screen.width * .5f, Screen.height * .4f), "Score: " + score);
     }
 
 }