Brick Game getting error

I am trying to maek brick breaker game i can move paddle but the problem When press play button the ball is not come down and i also getting error on my ball script

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Ballcontrol : MonoBehaviour
6. {
7.     public Vector2 currentVel;
8.     public Vector2 ballvel;
9.  
10.     // Start is called before the first frame update
11.     void Start()
12.     {
13.         ballvel = new Vector2(3, -3);
14.         GetComponent<Rigidbody>().velocity = ballvel;
15.  
16.     }
17.  
18.     // Update is called once per frame
19.     void Update()
20.     {
21.         currentVel = GetComponent<Rigidbody2D>().velocity;
22.         if (currentVel.y > 6)
23.         {
24.             GetComponent<Rigidbody2D>().velocity = new Vector2(currentVel.x, 6);
25.         }
26.         if (currentVel.y < -6)
27.         {
28.             GetComponent<Rigidbody2D>().velocity = new Vector2(currentVel.x, -6);
29.         }
30.         if (currentVel.x > 6)
31.         {
32.             GetComponent<Rigidbody2D>().velocity = new Vector2(6, currentVel.y);
33.         }
34.  
35.         if (currentVel.x < -6)
36.         {
37.             GetComponent<Rigidbody2D>().velocity = new Vector2(-6, currentVel.y);
38.         }
39.     }
40.     void OnCollisionEnter2D(Collision2D Other)
41.  
42.     {
43.         if (Other.gameObject.name == "Left")
44.         {
45.             GetComponent<Rigidbody2D>().velocity = new Vector2((currentVel.x * -1), (currentVel.y));
46.         }
47.         if (Other.gameObject.name == "Right")
48.         {
49.             GetComponent<Rigidbody2D>().velocity = new Vector2((currentVel.x * -1), (currentVel.y));
50.         }
51.  
52.     }
53. }
54.