2d Spaceship smooth mouse movement

I'm using a mosue to move my player on a 2d spaceship game.

 void FixedUpdate ()
 {
     float moveHorizontal = Input.GetAxis ("Mouse X") * speedx;
     float moveVertical = Input.GetAxis ("Mouse Y") * speedy;
     
     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
     GetComponent<Rigidbody> ().velocity = movement * speed;
     
     GetComponent<Rigidbody>().position = new Vector3 
         (
             Mathf.Clamp (GetComponent<Rigidbody>().position.x, boundary.xMin, boundary.xMax), 
             0.0f, 
             Mathf.Clamp (GetComponent<Rigidbody>().position.z, boundary.zMin, boundary.zMax)
             );
     
     GetComponent<Rigidbody>().rotation = Quaternion.Euler (0.0f, 0.0f, GetComponent<Rigidbody>().velocity.x * -tilt);
 }

I've added a float (speedx and speedy) to speed up the movement because it wasn't following my mouse enough quickly. When it comes on the boundary, the ship is kind of lagy a lil. I'm new in coding so I would realy apreciate any help to fix the smoothness of the ship!