GameManager example

GameManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class GameManager : MonoBehaviour {

	private static GameManager instance;

	public static GameManager Instance { get { return instance; } }

	[SerializeField]
    private int startingShips = 4;
	private int _actualShips;

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

	// Use this for initialization
	void Start () {
		ResetGameValues();
	}
	
	// Update is called once per frame
	void Update () {
		
	}

	private void ResetGameValues () {
		_actualShips = startingShips;
	}

	public int GetShips () {
		return _actualShips;
	}

	public void RemoveShip () {
		_actualShips--;
	}
}