MainMenu.cs

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

public class MainMenu : MonoBehaviour
{
 public string startLevel;// Updated to use SceneManager
 public string levelSelect; // Updated to use SceneManager
 public int playerHealth;// Set the player's health to the playerHealth variable


 public int playerLives;
 public void NewGame()
 {
    // Application.LoadLevel(startLevel);
    SceneManager.LoadScene(startLevel);

    PlayerPrefs.SetInt("PlayerCurrentLives", playerLives);

    PlayerPrefs.SetInt("PlayerCurrentScore", 0);

    PlayerPrefs.SetInt("PlayerCurrentHealth", playerHealth); // Set the player's health to the playerHealth variable
    PlayerPrefs.SetInt("PlayerMaxHealth", playerHealth);// Set the player's health to the playerHealth variable



 }

 public void LevelSelect()
 {
   PlayerPrefs.SetInt("PlayerCurrentLives", playerLives);// Set the player's lives in the PlayerPrefs

   PlayerPrefs.SetInt("PlayerCurrentScore", 0);// Set the player's score in the PlayerPrefs

   PlayerPrefs.SetInt("PlayerCurrentHealth", playerHealth); // Set the player's health to the playerHealth variable
   PlayerPrefs.SetInt("PlayerMaxHealth", playerHealth);// Set the player's health to the playerHealth variable


    // Application.LoadLevel(levelSelect);
    SceneManager.LoadScene(levelSelect);

 }

 public void QuitGame()
 {
     Application.Quit();
 }

}