Mario Powerups Switching problem,Mario PowerUps Switch problem

Hello, my name is Reno. I am a beginner in programming and I want to program a game. My first game is a Mario Clone. I programmed it so that there is a game object for each powerup form. Each time Luigi touches the mushroom, the game object has to be changed. My problem is that when Luigi touches the mushroom, the gameobjects are switching nonstop per milisecond. Its kinda hard to explain.

I hope you understand what I mean. When Luigi touches the mushroom he should switch with the big gameobject and stay in that form. Now they are switching betwen those two.

This is my Code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 
 public class Collecter : MonoBehaviour
 {
     public GameObject LilMario, BigMario;
 
     int whichMarioIsOn = 1;
 
     void Start()
     {
         
         LilMario.gameObject.SetActive(true);
         BigMario.gameObject.SetActive(false);
         
     }
     void Update()
     {
         SwitchMario();
     }
 
     public void SwitchMario()
     {
         switch (whichMarioIsOn)
         {
             //Default case
             case 1:
 
                 whichMarioIsOn = 1;
 
                 LilMario.gameObject.SetActive(true);
                 BigMario.gameObject.SetActive(false);
                 break;
             //Big case
             case 2:
 
                 whichMarioIsOn = 2;
 
                 LilMario.gameObject.SetActive(false);
                 BigMario.gameObject.SetActive(true);
                 break;
          }
     }
 
 
 
     private void OnCollisionEnter2D(Collision2D other)
     {
         if (other.gameObject.tag == "Pilz")
         {
             whichMarioIsOn = 2;
             Debug.Log("2 aktiv");
             Destroy(other.gameObject);
             
         }
     }
 
     
 
 
 
 
 
 
 
 
 }
 

I think the problem is in the update method. I hope you understand it and can help me. Thx for every answers have a nice day !,Hello, my name is Reno. I am a beginner in programming and I want to program a game. My first game is a Mario Clone. I programmed it so that there is a game object for each powerup form. Each time Luigi touches the mushroom, the game object has to be changed. My problem is that when Luigi touches the mushroom, the gameobjects are switching nonstop per milisecond. Its kinda hard to explain.

I hope you can understand what I mean. I want that when Luigi touches should the bigLuigi appear and stay. But now both are switching nonstop.

This is my Code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 
 public class Collecter : MonoBehaviour
 {
     public GameObject LilMario, BigMario;
 
     int whichMarioIsOn = 1;
 
     void Start()
     {
         
         LilMario.gameObject.SetActive(true);
         BigMario.gameObject.SetActive(false);
         
     }
     void Update()
     {
         SwitchMario();
     }
 
     public void SwitchMario()
     {
         switch (whichMarioIsOn)
         {
             //Default case
             case 1:
 
                 whichMarioIsOn = 1;
 
                 LilMario.gameObject.SetActive(true);
                 BigMario.gameObject.SetActive(false);
                 break;
             //Big case
             case 2:
 
                 whichMarioIsOn = 2;
 
                 LilMario.gameObject.SetActive(false);
                 BigMario.gameObject.SetActive(true);
                 break;
          }
     }
 
 
 
     private void OnCollisionEnter2D(Collision2D other)
     {
         if (other.gameObject.tag == "Pilz")
         {
             whichMarioIsOn = 2;
             Debug.Log("2 aktiv");
             Destroy(other.gameObject);
             
         }
     }
 
     
 
 
 
 
 
 
 
 
 }
 

I think the problem is in the void Update Method. I hope you can help me. Thx for every Answer.