Power up not working

Hello I'm making a game like "ballz", for the first time I'm making powerUps in a game so I don't have a brief background about it, so what I need is when the ball hit a brick if the brick health is 5 and the powerUp takes from the health 5 so in one hit it will destroy the brick!, I tried a lot to make it work for me, I tried a lot to make it work but no result. Here in this code when I debug the game it's giving me true which is the powerUp it's working but it's not taking 5 from the health of the brick. SOMEBODY HELP PLEASE!

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class powerUp: MonoBehaviour {
 
     public bool powerUp = false;
     private BrickHealthManager HpManager;
 
     void Start()
     {
         powerUp = true;
         HpManager = FindObjectOfType<BrickHealthManager>();
     }
 
 
     private void OnTriggerEnter2D(Collider2D other)
     {
         if (other.gameObject.tag == "Ball")
         {
             Debug.Log(powerUp);
             powerUp = true;
             this.gameObject.SetActive(false);
         }
     }
 
     void OnCollisionExit2D(Collision2D other)
     {
         if (other.gameObject.tag == "Ball") 
         {
             TakeDamage (5);
         }
     }
 }
 

BrickHealthManager script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class BrickHealthManager : MonoBehaviour {
 
     public GameObject brickDestroy;
     public int brickHealth;
     private Text brickHealthText;
     private GameManager gameManager;
     private ScoreManager score;
     private SkillCoin skillCoin;
 
     // Use this for initialization
     void Start () 
     {
         skillCoin = GetComponent<SkillCoin>();
         score = FindObjectOfType<ScoreManager>();
         gameManager = FindObjectOfType<GameManager> ();
         brickHealth = gameManager.level;
         brickHealthText = GetComponentInChildren<Text> ();
 
     }
 
     void OnEnable()
     {
         gameManager = FindObjectOfType<GameManager> ();
         brickHealth = gameManager.level;
     }
 
     // Update is called once per frame
     void Update () 
     {
         brickHealthText.text = "" + brickHealth;
         if (brickHealth <= 0) {
             //Destroy Brick
             score.IncreaseScore();
             this.gameObject.SetActive(false);
             Instantiate(brickDestroy, transform.position, Quaternion.identity);
         }
     }
 
     public void TakeDamage(int damageToTake)
     {
         brickHealth -= damageToTake;
     }
 
     void OnCollisionExit2D(Collision2D other)
     {
         if (other.gameObject.tag == "Ball" || other.gameObject.tag == "Extra Ball") 
         {
             TakeDamage (1);
         }
     }
 }