3DTD/Assets/Scripts/UI/PlayerHealth.cs

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

public class PlayerHealth : MonoBehaviour
{
    public GameObject gameOver;
    public TMP_Text text;

    void Update()
    {
        text.text = $"{GameManager.Instance.health} / {GameManager.Instance.startHealth}";

        if (GameManager.Instance.health <= 0)
        {
            StartCoroutine(GameOver());
        }
    }

    private IEnumerator GameOver()
    {
        gameOver.SetActive(true);
        yield return new WaitForSecondsRealtime(5f);
        SceneManager.LoadScene(0);
    }

}