How to make automatically moving sprite not passing through another sprite?

I have made a scene like the above picture. The wall is made by a number of tiles. The bomb has set a c# script to move automatically like this: using UnityEngine;

 public class BombScript : MonoBehaviour {
 
     public int speedX;
     public int speedY;
     public int directionX;
     public int directionY;
     public Vector2 speed;
     public Vector2 direction;
     public Vector2 movement;
     public bool collided = false;
 
     void Start () {
         speedX = Random.Range (1, 3);
         speedY = Random.Range (1, 3);
         directionX = Random.Range (-1, 1);
         directionY = Random.Range (-1, 1);
         while (directionX == 0 && directionY == 0) {
             directionY = Random.Range (-1, 1);
         }
         speed = new Vector2 (speedX, speedY);
         direction = new Vector2 (directionX, directionY);
     }
 
     void Update () {
         movement = new Vector2 (speed.x * direction.x, speed.y * direction.y);
 
     }
 
     void FixedUpdate() {
         rigidbody2D.velocity = movement;
 
     }
 
 }

I give the wall box collider 2D and the bomb circle collider 2D, rigid body of 0 gravity and physic 2D for bouncing. But when I run it, the bomb didn't bounce or stop by the walls but passed through the walls. How can I fix it to make the bomb bounce?