❔ Newbie Q: Preventing double jump in unity

public class CatMovement : MonoBehaviour
{
    public bool OnGround = true;

    // Start is called before the first frame update
    void Start()
    {
    }

    // Update is called once per frame
    void Update()
    {
        Rigidbody2D body = GetComponent<Rigidbody2D>();
        if (Input.GetKey(KeyCode.UpArrow) && OnGround)
        {
            // Getting the rigidbody component of the sprite - vector 3 since using 3 values (x,y,z) 
            // GetComponent<Rigidbody2D>().velocity = new Vector3(0, 10, 0);
            body.AddRelativeForce(new Vector2(0, 1000));
            this.OnGround = false;
        }
        if (Input.GetKey(KeyCode.RightArrow))
        {
            body.AddRelativeForce(new Vector2(50, 0));
        }
        if (Input.GetKey(KeyCode.LeftArrow))
        {
            body.AddRelativeForce(new Vector2(-50, 0));
        }
    }
}

public class GroundDetection : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {
        GameObject cat = GameObject.FindWithTag("Cat");
        transform.position = cat.transform.position;
    }

    // Update is called once per frame
    void Update()
    {
    }
    void OnCollisionEnter2D(Collision2D col)
    {
        Debug.Log("Ok");
        CatMovement movement = GetComponent<CatMovement>();
        movement.OnGround = true;
    }
}