Three ingame buttons conflict with each other on iOS

I'm just learning Unity and I would like to ask a pretty simple question. I have 3 buttons in my class and they work strange. Here's how I create them:

  void OnGUI() {
         
         if (GUI.RepeatButton(new Rect(10, 440, 120, 180), @"Left"))
             //Debug.Log("Clicked left");
         goLeft();
         
         if (GUI.RepeatButton(new Rect(820, 440, 120, 180), "Right"))
             //Debug.Log("Clicked right");
         goRight();
         
         if (GUI.Button(new Rect(410, 440, 200, 200), "Shoot"))
         TapFunction();
     }

And they trigger 3 methods as you can see:

     void goLeft() {
         Debug.Log("Clicked left");
                     if (transform.position.x < -20) {
     //get new speed
     speed = Random.Range(8f,12f);
     transform.position = new Vector3( 20f, transform.position.y, transform.position.z );
 }        
 transform.Translate(0, 0, -speed * Time.deltaTime);
 
     }
     
     void goRight() {
         Debug.Log("Clicked right");
                         if (transform.position.x > 20) {
     //get new speed
     speed = Random.Range(8f,12f);
     transform.position = new Vector3( -20f, transform.position.y, transform.position.z );
 }        
 transform.Translate(0, 0, speed * Time.deltaTime);
     }
     
     void TapFunction() {
     GameObject bombObject = (GameObject)Instantiate(bombPrefab);
     bombObject.transform.position = this.gameObject.transform.position;
 }

The peculiar thing is that when I touch on the button and anywhere else on the screen with another finger, the button I was holding my finger on becomes inactive. When touching another button while holding another one, the 2nd button (one with the type GUI.Button) is fired.

How can I make 2 GUI.RepeatButtons cancel each other (so when I press on the first one while pressing on the second, the first one would release the touch?) and the GUI.Button not get fired on touch with another button?