BallControl.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BallControl : MonoBehaviour
{
    private Rigidbody2D rb2d;

    void GoBall() {
        float rand = Random.Range(0, 2);
        if (rand < 1) {
            rb2d.AddForce(new Vector2(20, -15));
        }
        else {
            rb2d.AddForce(new Vector2(-20, -15));
        }
    }

    // Start is called before the first frame update
    void Start(){
        rb2d = GetComponent<Rigidbody2D>();
    }

    void ResetBall() {
        rb2d.velocity = Vector2.zero;
        transform.position = Vector2.zero;
    }

    void RestartGame() {
        ResetBall();
        Invoke("GoBall", 1);
    }

    void OnCollisionEnter2D(Collision2D coll) {
		if (coll.collider.CompareTag ("Player")) {
			Vector2 vel;
			vel.x = rb2d.velocity.x;
			vel.y = (rb2d.velocity.y / 2.0f) + (coll.collider.attachedRigidbody.velocity.y / 3.0f);
			rb2d.velocity = vel;
		}
	}
}