Simple ball bounce (like pang/bubble trouble)

To answer my own question:

This is very easy to do. First mistake I did was use physics materials. No need for those here. Other than that - just using hit normal did the trick.

 private float velX = 1.9f;//horizontal speed of ball
 private Vector2 Vel_in;//save incoming velocity here

 private float startY;//max jump height (every time ball hits floor it will calculate force needed to reach this height).


 void FixedUpdate()
 {
     Vel_in = rigidbody2D.velocity;
  }

  void OnCollisionEnter2D(Collision2D coll)
  {

     ContactPoint2D hit = coll.contacts[0]; //(for debug only) the first contact is enough
     Vector3 Vel_out = Vector3.Reflect(Vel_in, hit.normal);

     if(hit.normal.x < 0)
         rigidbody2D.velocity = new Vector2( - velX, Vel_in.y);
     else if(hit.normal.x > 0)
         rigidbody2D.velocity = new Vector2( velX, Vel_in.y);
     else
         rigidbody2D.velocity = new Vector2( velX*(Vel_in.x/Mathf.Abs(Vel_in.x)), rigidbody2D.velocity.y);

     if(hit.normal.y < 0)
     {
         if (Mathf.Abs(Vel_in.y) < 1)
             rigidbody2D.velocity = new Vector2( rigidbody2D.velocity.x, -1);
         else
             rigidbody2D.velocity = new Vector2( rigidbody2D.velocity.x, -Mathf.Abs(Vel_in.y));

     } else if(hit.normal.y > 0)
     {     //jumping up, calculate how much force is needed to jump to certain height (startY)
         float relPos = transform.position.y - startY;
         if(relPos > 0f)
             relPos = 0f;
         float newYVel = Mathf.Sqrt(2 * relPos * Physics2D.gravity.y * rigidbody2D.gravityScale);
         if (newYVel == 0) newYVel = 1f;
         rigidbody2D.velocity = new Vector2( rigidbody2D.velocity.x, newYVel);
     }


     //save now, because sometimes collision happens before next FixedUpdate tick
     Vel_in = rigidbody2D.velocity;
 }