Once my charachter touches the groun isGorund stays on

Im new to making games, csharp and unity. I followed this tutorial I found online and followed the code but I ran into a problem. The guy made a code that you can jump in midair infinatly amount of times. Then he fixed the problem by adding some code that I followed and copied. Now I have this problem where if my character touches the ground once it will think hes touching it all the time. Pls help and thanks. I have 2 codes.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Movement : MonoBehaviour
6. {
7.     public float moveSpeed = 5f;
8.     public float jumpForce = 5f;
9.     public bool isGrounded = false;
10.     // Start is called before the first frame update
11.     void Start()
12.     {
13.        
14.     }
15.  
16.     // Update is called once per frame
17.     void Update()
18.     {
19.         Jump();
20.         Vector3 movement = new Vector3(Input.GetAxis("Horizontal"), 0f, 0f);
21.         transform.position += movement * Time.deltaTime * moveSpeed;
22.     }
23.  
24.     void Jump()
25.     {
26.         if (Input.GetButtonDown("Jump") && isGrounded == true)
27.         {
28.             gameObject.GetComponent<Rigidbody2D>().AddForce(new Vector2(0f, jumpForce), ForceMode2D.Impulse);
29.  
30.         }
31.        
32.     }
33.  
34. }
35.  

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class TlaPreveri : MonoBehaviour
6. {
7.     GameObject Junak;//lohka da bo problem
8.     // Start is called before the first frame update
9.     void Start()
10.     {
11.         Junak = gameObject.transform.parent.gameObject;
12.     }
13.  
14.     // Update is called once per frame
15.     void Update()
16.     {
17.        
18.     }
19.     private void OnCollisionEnter2D(Collision2D collision)
20.     {
21.         if(collision.collider.tag == "Ground")
22.         {
23.             Junak.GetComponent<Movement>().isGrounded = true;
24.         }
25.     }
26.  
27.     private void OnCollisionExit(Collision collision)
28.     {
29.         if (collision.collider.tag == "Ground")
30.         {
31.             Junak.GetComponent<Movement>().isGrounded = false;
32.         }
33.     }
34. }
35.  

 

You are using OnColissionExit (I guess you have a 2D game with 2D collider). Try using OnCollisionExit2D(Collission2D collision)