ExtraLife.cs

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

public class ExtraLife : MonoBehaviour
{

    private LifeManager lifeStystem;
    // Start is called before the first frame update
    void Start()
    {
        lifeStystem = FindObjectOfType<LifeManager>();

    }

   void OnTriggerEnter2D(Collider2D other)
    {
        if (other.name == "Player")
        {
            lifeStystem.AddLife();

            Destroy(gameObject);
        }
    }
}