mouse position in world point and player direction

        if (MoveByTouch) 
        {   
            float deltaTime = Time.deltaTime;    
            float speed = runSpeed * deltaTime;
            r_Zpos += speed;            
            Vector3 mousePos = Input.mousePosition;
            mousePos.z = r_Zpos;
            Vector3 pos =  _camera.ScreenToWorldPoint(mousePos);
            r_XPos = Mathf.Lerp(r_XPos, pos.x, deltaTime * swipeSpeed);
        }
        r_transform.position = new Vector3(r_XPos, 0f, r_Zpos);
        if (r_transform.position != r_LastPosition)
        {
            r_transform.forward = Vector3.Lerp(r_transform.forward, (r_transform.position - r_LastPosition).normalized,
                speed);
        }

        r_LastPosition = r_transform.position;

I can't really find the problem here, I want my player follow the mouse position but still facing to the camera. but the player keep facing the mouse direction.
does anyone have any solution? thank you for taking your time!

You say that you don't want the player to face the mouse position, but you are doing so by setting r_transform.forward=... in your code.

If your goal is to make the player face the camera, that is a rotational problem. transform.forward is connected to rotation as well though.
Try setting the transform.position to the world position of your mouse as you already tried and make the player face the camera independantly by manipulating transform.rotation.

If you must set the transform.forward in relation to your mouse position, you can try to make a child object in your player for visual representation and make that child face the camera while the parent moves as you like.

Maybe have a look at this to learn how to make objects look at something: https://docs.unity3d.com/ScriptReference/Transform.LookAt.html