Save button state using Playerprefs

Hi.
I'm making Android Clicker Game.
I want to save my button state on the DataController GameObject which controls all the data.
Everything works fine except data saving.
I want to make data automatically saved when I exit the game.
Here is the scripts.

Button Script(This controls the button. Also brings and saves the data from and on the DataController)

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class BGMBuy : MonoBehaviour {
 
     public AudioSource sound;
     public string bgmName;
     public Button BGM;
     public Button Disabled;
     public int currentCost;
     [HideInInspector]
     public int butdisable;
     public bool bought;
 
 
     void Start()
     {
         DataController.Instance.LoadBGMBuy (this);
         bought = false;
     }
 
     public void PurchaseMusic ()
     {
         if (DataController.Instance.gold >= currentCost) 
         {
             if (bought == false) 
             {
                 DataController.Instance.gold -= currentCost;
                 PlayerPrefs.SetInt ("butdisable", 1);
                 sound.Play ();
                 BGM.interactable = true;
                 Disabled.interactable = false;
 
                 DataController.Instance.SaveBGMBuy (this);
 
 
             }
 
             else 
             {
                 Disabled.interactable = true;
 
             }
         }
     
     }
 }

DataController Script(This controls all the data. Every datas are saved here. Other scripts are used to bring the data from here)

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class DataController : MonoBehaviour {
 
 
     private static DataController instance;
 
 
     public static DataController Instance 
     {
         get 
         {
             if (instance == null) 
             {
                 instance = FindObjectOfType<DataController> ();
                 if (instance == null) 
                 {
                     GameObject container = new GameObject ("DataController");
                     instance = container.AddComponent<DataController> ();
                 }
             }
             return instance;
         }
     }
 
 
     private ItemButton[] itemButtons;
 
 
     public long gold 
     {
         get 
         {
             if (!PlayerPrefs.HasKey ("Gold")) 
             {
                 return 0;
             }
 
             string tmpGold = PlayerPrefs.GetString ("Gold");
             return long.Parse (tmpGold);
         }
             
         set
         { 
             PlayerPrefs.SetString ("Gold", value.ToString());
         }
     }
 
     public int goldPerClick
     {
         get
         {
             return PlayerPrefs.GetInt("GoldPerClick",1);
         }
 
         set
         { 
             PlayerPrefs.SetInt ("GoldPerClick", value);
 
         }
     }
     void Awake()
     {
         //PlayerPrefs.DeleteAll ();
 
 
         itemButtons = FindObjectsOfType <ItemButton> ();
     }
 
 
 
 
 
     public void LoadUpgradeButton(UpgradeButton upgradeButton)
     {
         string key = upgradeButton.upgradeName;
 
         upgradeButton.level = PlayerPrefs.GetInt (key + "_level", 1);
         upgradeButton.goldByUpgrade = PlayerPrefs.GetInt (key + "_goldByUpgrade", upgradeButton.startGoldByUpgrade);
         upgradeButton.currentCost = PlayerPrefs.GetInt (key + "_cost", upgradeButton.startCurrentCost);
     }
 
     public void SaveUpgradeButton(UpgradeButton upgradeButton)
     {
         string key = upgradeButton.upgradeName;
 
         PlayerPrefs.SetInt (key + "_level", upgradeButton.level);
         PlayerPrefs.SetInt (key + "_goldByUpgrade", upgradeButton.goldByUpgrade);
         PlayerPrefs.SetInt (key + "_cost", upgradeButton.currentCost);
     }
 
     public void LoadItemButton(ItemButton itemButton)
     {
         string key = itemButton.itemName;
 
         itemButton.level = PlayerPrefs.GetInt(key + "_level");
         itemButton.currentCost = PlayerPrefs.GetInt (key + "_cost", itemButton.startCurrentCost);
         itemButton.goldPerSec = PlayerPrefs.GetInt (key + "_goldPerSec");
 
         if (PlayerPrefs.GetInt (key + "_isPurchased") == 1) 
         {
             itemButton.isPurchased = true;
         } 
         else 
         {
             itemButton.isPurchased = false;
         }
     }
 
     public void SaveItemButton(ItemButton itemButton)
     {
         string key = itemButton.itemName;
 
         PlayerPrefs.SetInt(key + "_level",itemButton.level);
         PlayerPrefs.SetInt (key + "_cost", itemButton.currentCost);
         PlayerPrefs.SetInt (key + "_goldPerSec",itemButton.goldPerSec);
 
         if (itemButton.isPurchased == true) 
         {
             PlayerPrefs.SetInt (key + "_isPurchased", 1);
         } 
         else 
         {
             PlayerPrefs.SetInt (key + "_isPurchased", 0);
         }
         
     }
 
     public int GetGoldPerSec()
     {
         int goldPerSec = 0;
         for (int i = 0; i < itemButtons.Length; i++) 
         {
             goldPerSec += itemButtons [i].goldPerSec;
         }
 
         return goldPerSec;
     }
 
     public void LoadBGMBuy(BGMBuy bgmBuy)
     {
         string key = bgmBuy.bgmName;
 
         bgmBuy.butdisable = PlayerPrefs.GetInt (key + "bought");
 
         if(bgmBuy.bought == true)
         {
             PlayerPrefs.GetInt (key + "_bought",1);
         }
 
         else
         {
             PlayerPrefs.GetInt (key + "_bought",0) ;
         }
     }
 
     public void SaveBGMBuy(BGMBuy bgmBuy)
     {
         string key = bgmBuy.bgmName;
 
         PlayerPrefs.SetInt (key + "_bought", bgmBuy.butdisable);
 
         if(bgmBuy.bought == true)
         {
             PlayerPrefs.SetInt (key + "_bought",1);
         }
 
         else
         {
             PlayerPrefs.SetInt (key + "_bought",0) ;
         }
 
     }
 }