Question Unity Game: An object reference is required for the non-static field, method, or property

I want to start this by pointing out that I'm a beginner in C#. I'm doing this for just a week.
I started creating a game in Unity and today I tried to make a save/load system for it.


I followed a tutorial, did all the steps but at the final, i get this error:

Game.cs(22,9): error CS0120: An object reference is required for the non-static field, method, or property 'Game.coal'

Here are the important parts of Game.cs

Code (CSharp):

1. public class Game : MonoBehaviour
2. {  
3.     public int coal = 0;
4.     public int multiplier = 1;
5.     public int upgradeprice = 10;
6.     public int coalprice = 1;
7.     public int uplvl = 1;
8.     public int money = 1;

...

The void where I got this error:

Code (CSharp):

1.     public void Increment() {
2.         Game.coal += Game.multiplier;
3.         PlayerPrefs.SetInt("coal", Game.coal);
4.     }

This void Increment is connected to a game object, where everytime I click it, i need to increase my coal.

If I set my `public int ` to `public static int`, I get another error in my other script:
PlayerData.cs(16,16): error CS0176: Member 'Game.coal' cannot be accessed with an instance reference; qualify it with a type name instead

My PlayerData script:

Code (CSharp):

1. public class PlayerData
2. {
3.     public int coal;
4.     public int multiplier;
5.     public int upgradeprice;
6.     public int coalprice;
7.     public int uplvl;
8.     public int money;
9.  
10.     public PlayerData (Game m) {
11.         coal = m.coal;
12.         multiplier = m.multiplier;
13.         upgradeprice = m.upgradeprice;
14.         coalprice = m.coalprice;
15.         uplvl = m.uplvl;
16.         money = m.money;
17.     }
18. }

I'm sorry If i formatted the text wrong but I'm new on this platform. If anyone can help me i'll be grateful.