Bullet ricochet 2D not working

Hello, I've tried to get my projectile bullet to work for so long but I just couldn't make it work so now I'm asking for help. It just doesn't bounce at all or bounces in the complete wrong direction. Here's the code:

 void Update () {
         rb.angularVelocity = 0;
         rb.velocity = transform.up * (P1BulletSpeed / 2);
     }
 
     void OnCollisionEnter2D(Collision2D collision) {
         if (collision.gameObject.tag == "Tank") {
             print ("b");
         } else if (collision.gameObject.tag == "Wall" || collision.gameObject.tag == "DWall"){
             Vector2 reflectedPosition = Vector2.Reflect(transform.up, collision.contacts[0].normal);
             rb.velocity = (reflectedPosition).normalized * (P1BulletSpeed / 2);
             Vector2 dir = rb.velocity;
             float angle = Mathf.Atan2(dir.y, dir.x) * Mathf.Rad2Deg;
             rb.MoveRotation(angle);
         }
     }