分数在下一级别被覆盖。有人可以帮我吗

Question

玩家启动并收集燃料罐，燃料存放在更大的油箱中，然后加载下一张地图。收集的燃料设置为 0。在第二张地图中，收集了燃料，但当你存放它时，分数将被覆盖，而不是添加到。

using UnityEngine;
using UnityEngine.UI;

public class ScoreManager : MonoBehaviour
{
    public static ScoreManager instance;

    //script refs
    GasTransfer gt;
    LevelLoader levelLoader;
    //text refs
    public Text ScoreText;
    public Text StoredFuel;
    //bools ints
    public int collectedfuel = 0;
    private int score;
    public int storedFuel;
    public bool fuelDelivered;

    private void Awake()
    {
        if (instance == null)
        {
            instance = this;
            DontDestroyOnLoad(gameObject);
        }
        else if (instance != null)
            Destroy(gameObject);

    }
    public void Start()
    {
        gt = FindObjectOfType<GasTransfer>();
        levelLoader = FindObjectOfType<LevelLoader>();
        
    }

    // Update is called once per frame
    public void Update()
    {
        ScoreText.text = collectedfuel.ToString();

        if (Input.GetKey(KeyCode.F) && gt.isAtpump)
        {
            score = collectedfuel = storedFuel;
            storedFuel = collectedfuel;
            StoredFuel.text = score.ToString();
            fuelDelivered = true;

        }
         
        if (fuelDelivered)
        {
            gt.pressF.SetActive(false);
            levelLoader.LoadNextLevel();

        }
    }


    public void AddFuel() 
    {
        collectedfuel += 5;
    }

    public void RemoveFuel()
    {
        collectedfuel -= 5;

        if(collectedfuel < 0)
           collectedfuel = 0;
    }



    
}

看了几个视频，教程，unity教程。这就是我走到这一步的方式。我只是找不到合适的单词组合来添加到现有分数中。