In Game Shop

Hello guys what's up i was working in game unity shop and i thought you guys can help me with something,have you ever play color switch or any Ketchapp game? if yes than you saw that in almost everygame there is a shop and i want to make a shop in that way here is my script...yes my scrip its working but i have a problem. when i buy an item it equipts it but i want my money to be -100 and and then to save that i bought that skin can someone help ? :) thank you all

public class Shopmenager : MonoBehaviour { private static int playerMoney; private Text MoneyHud; #region ItemConfig public Image itemIcon; public Text itemCost; public Text itemName; public int buttonIndex; public string ItemName; public string ItemCost; public Sprite ItemIcon; public Sprite BallIcon; public Sprite CointIcon; public Sprite bgWhite; public Sprite noBg; private Image backgroundImg; #endregion

 string skinName = string.Empty;
 private GameObject[] items;
 void Start()
 {
     playerMoney = PlayerPrefs.GetInt("Coints");
     skinName = PlayerPrefs.GetString("PlayerSprite");
     backgroundImg = GetComponent<Image>();
     items = GameObject.FindGameObjectsWithTag("item");
     MoneyHud = GameObject.FindGameObjectWithTag("HudCoins").GetComponent<Text>();
     itemName.text = ItemName;
     itemCost.text = ItemCost;
     itemIcon.sprite = ItemIcon;
 }
 void Update()
 {
     Debug.Log(MoneyHud);
     print(skinName + " " + ItemName);

     if (backgroundImg.sprite.name == bgWhite.name && skinName != ItemName)
     {
         print("Changing "+ItemName);
         
         backgroundImg.sprite = noBg;
     }
 }
 public void On_Click_Button()
 {
     int skin_buyed = 0;
     playerMoney = PlayerPrefs.GetInt("Coints");
     int val = playerMoney - Convert.ToInt32(ItemCost);
      print(playerMoney + " - " + ItemCost + " = " + val);
     if (val >= 0)
     {
         if (canBuy())
         {
             playerMoney = val;
             if (playerMoney <= 0)
             {
                 playerMoney = 0;
             }
             MoneyHud.text = playerMoney.ToString();
         }
         else
         {
             print("You already have this item.");
         }
         switch (buttonIndex)
         {
             case 1:
                 PlayerPrefs.SetString("PlayerSprite", null);
                 PlayerPrefs.SetString("EnemySprite", "Point");
                 break;
             case 2:
                 skin_buyed = PlayerPrefs.GetInt("Skin2");
                 skin_buyed = PlayerPrefs.GetInt("Point2"); 

                 if (skin_buyed == 1)
                 {
                     PlayerPrefs.SetString("PlayerSprite", "Skin3");
                     PlayerPrefs.SetInt("Skin2", 1);
                     itemIcon.sprite = CointIcon;
                     PlayerPrefs.SetString("EnemySprite", "Point3");
                     PlayerPrefs.SetInt("Point2", 1);
                 }
                 else
                 {
                     print("You already buyed this item.");
                 }
                 break;
             case 3:
                 skin_buyed = PlayerPrefs.GetInt("Skin3");
                 skin_buyed = PlayerPrefs.GetInt("Point3");
                 if (skin_buyed == 1)
                 {
                     PlayerPrefs.SetString("PlayerSprite", "Skin3");
                     PlayerPrefs.SetInt("Skin3", 1);
                     itemIcon.sprite = CointIcon;
                     PlayerPrefs.SetString("EnemySprite", "Point3");
                     PlayerPrefs.SetInt("Point3", 1);
                 }
                 else
                 {
                     print("You already buyed this item.");
                 }
             default:
                 break;
         }
         skinName = PlayerPrefs.GetString("PlayerSprite");
         print(skinName);
         foreach(GameObject i in items)
         {
             Image img = i.GetComponent<Image>();
             img.sprite = noBg;
         }
         if (skinName == ItemName)
         {
             backgroundImg.sprite = bgWhite;
             itemIcon.sprite = BallIcon;
             itemName.text = string.Empty;
             itemCost.text = string.Empty;
         }
     }
     else
     {
         print("You dont have enough coins " + ItemCost);
     }
     PlayerPrefs.SetInt("Coints", playerMoney);
 }

 public bool canBuy()
 {  
     

     bool ok = true;
     int skin_buyed = 0;
     switch (buttonIndex)
     {
         case 1:
             
             break;
         case 2:
             skin_buyed = PlayerPrefs.GetInt("Skin2");
             if (skin_buyed == 1)
             {
                 ok = false;
             }
             break;
         case 3:
             skin_buyed = PlayerPrefs.GetInt("Skin3");
             if (skin_buyed == 1)
             {
                 ok = false;
             }
             break;
         default:
             break;
     }
     return ok;
 }

}