How to Save the Current that what load from playerprefs

I am making a shop where player can earn money by kill the enemy, i getting it to save and be update on the shop menu but when i create a function to minus the money to see if it would change,but it would not even changing keep giving me the same amount of money i save but when i create the minus function in the save script it work good but i don't it to be there, need of help Please

using UnityEngine; using System.Collections; using UnityEngine.UI;

public class MoneyManager : MonoBehaviour {

 public  int money;
 public int currMoney;
 public Text moneyText;
 public  int addmoney;
 //public Text ShopMoney;
 //public static int Money;

 Text text;
 void Start () {
     money = PlayerPrefs.GetInt("EarnM");
     currMoney = money;
     //money = 0;
     //currMoney = PlayerPrefs.GetInt("money");
     
     //moneyText = GetComponent<Text> ();

     //currMoney = PlayerPrefs.GetInt ("EarnM",0);
     //money = currMoney;

     //currMoney = PlayerPrefs.GetInt("money" + money);

 }


 // Update is called once per frame
 void Update () {
     moneyText.text = currMoney.ToString();
     //ShopMoney.text = Money.ToString ();
     //Money = money; 

     //money = PlayerPrefs.GetInt ("money");
     if (Input.GetButtonDown ("Fire2")) {
         PlayerPrefs.DeleteAll ();
     }
 }

 //public void AddMoney()
 //{
     //money += 20;
 //}


 void OnDestroy ()
 {
 
     //PlayerPrefs.SetInt ("money", currMoney);
     //PlayerPrefs.Save ();
 }

 public void Buy ()
 {
     currMoney--;

 }

}

and this is the save where i have it in a next scene just a ui setting creating some button to add money and minus money and the PlayerPrefs function

using UnityEngine; using System.Collections; using UnityEngine.SceneManagement; public class coins : MonoBehaviour {

 public int getcoin = 100;
 public  static int earnM;
 void Awake () {
 
 }
 
 // Update is called once per frame
 void Update () {
     if (Input.GetButtonDown ("Fire2")) {
         PlayerPrefs.DeleteAll ();
     }
 }

 public void AddCoin ()
 {
     earnM += getcoin;
     //OnGoal ();
 }


 void OnDestroy ()
 {
     PlayerPrefs.SetInt ("EarnM", PlayerPrefs.GetInt("EarnM")+ earnM);
     //PlayerPrefs.Save ();
     Debug.Log ("Saved");
 }

 public void LoadMainMenu()
 {
     SceneManager.LoadScene ("Main_Menu");
 }


 public void Buy ()
 {
     earnM--;
 }

}