Why after reflection my bullet falls out of the screen??

I have an object with Physics Material 2D .

My object rotates in four directions after pressing the left mouse button:

-up right

-down right

-down left

-up left

After pressing the right mouse button, my object should firing and bounce off the walls at an angle of 90 degrees in the direction of movement.

I don't understand why after a few reflections object falls out of the screen.

Could someone tell me why my bullet falls out of the screen?

To bounce at 90 degrees after hit I use:

 void OnCollisionEnter2D (Collision2D whatHitMe)
     {
         GameObject g = whatHitMe.gameObject;
            
                 if (g.CompareTag("Background") || g.CompareTag("Enemy"))
                     Debug.Log ("hit");
                 {
                        rb.velocity = Vector2.Reflect(currSpeed, whatHitMe.contacts[0].normal);
                     rb.rotation +=90;    
 
                 
         }
     }
 public void Update ()
 {

     currSpeed = new Vector2(rb.velocity.x, rb.velocity.y);
     }

To shoot the bullet after pressing the right mouse button I use:

 {
 
     if (Input.GetMouseButton(1)) {
         Debug.Log ("Pressed secondary button.");
         rightClicked = true;
         mouseClicked = false;
 
     }
     if(rightClicked)
 
 
         transform.position += (transform.right + transform.up).normalized *  speed * Time.deltaTime;
 
 }
 

For the rotation of the object in four direction I use:

 if (mouseClicked) {        //checks if sprite has already been changed
             Vector3 mousePos = Input.mousePosition;        //gets the current mouse position on screen 
             int currentCase = 0;
             //following does a case-check on the position of your mouse with respect to the sprite:
             if (Camera.main.transform.position.x - (Screen.width/2) + mousePos.x < transform.position.x) {        
                 if (Camera.main.transform.position.x - (Screen.height/2)+mousePos.y < transform.position.y) {
                     currentCase = 2;
                 } else {
                     currentCase = 3;
                 }
             } else {
                 if (Camera.main.transform.position.x - (Screen.height/2)+mousePos.y < transform.position.y) {
                     currentCase = 1;
                 } else {
                     currentCase = 0;
                 }
             }
             //create a new rotation:
             transform.rotation = Quaternion.Euler (0, 0, 90 * currentCase);
         }

PS1: If someone needs a full code, I put it in the attachment.

PS2: I put a video link that shows what the problem is.

 https://gfycat.com/pl/gifs/detail/AjarOffbeatDodobird

PS3: Forgive me that I only put the whole code in the attachment, but some people don't like when the long codes are posted :) :)

link text

I also noticed something:

If I add to the rb.rotation "+" the bullet is reflected only in the right side (which causes stuck or fall out when it should bounce left).

Analogous situation with a "-", but this time bullet reflected only left.

However without "+" or "-" bullet doesn't bounce at all.