Movement behaves differently on X axis

Hello,

I have a sprite that is supposed to look to the mouse and follow it, like a top-down game.

I have this script that adds 2 different velocities to the player. One for Y axis, and one for X axis. The problem is that the player has correct movement on the Y axis (when I look up it goes up with a speed of 1, when I look down it goes down with a speed of -1.) but on the X axis behaves weird...

 function Update () {
     var mousePos = Input.mousePosition;           
     mousePos = Camera.main.ScreenToWorldPoint(mousePos);
     var rot = Quaternion.LookRotation(transform.position - mousePos, Vector3.forward );
     transform.rotation = rot;  
     transform.eulerAngles = new Vector3(0, 0, transform.eulerAngles.z + 90);
     
     Debug.Log(transform.eulerAngles.z);

     // I use a function that calculates the correct speed for each axis.
     // For example when the player looks up-right (transform.eulerAngles.z = 45) y velocity should be 0.5 and x velocity should be 0.5.
     rigidbody2D.velocity.y = (90 - Mathf.Abs(transform.eulerAngles.z - 90))/90;
     rigidbody2D.velocity.x = (90 + Mathf.Abs(transform.eulerAngles.z - 90))/90 - 1;
 
     
 }

Any help?