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);
    }

}

PlayerPrefs.SetInt(“Score”, PlayerPrefs.GetInt(“Score”,0) + score);