void Update() {

    /* calculate rigidbody movement */
    movement = new Vector3( Input.GetAxisRaw("Horizontal"), 0, Input.GetAxisRaw("Vertical")).normalized;

    /* calculate mouse look to rotate the rigidbody*/
    mouseDelta = new Vector2(Input.GetAxisRaw("Mouse X"), Input.GetAxisRaw("Mouse Y"));
    mouseDelta = Vector2.Scale(mouseDelta, new Vector2(sensitivity * smoothing, sensitivity * smoothing));
    smoothV.x = Mathf.Lerp(smoothV.x, mouseDelta.x, 1f / smoothing);
    smoothV.y = Mathf.Lerp(smoothV.y, mouseDelta.y, 1f / smoothing);
    mouseLook += smoothV;

}

void FixedUpdate() {

    /* apply rigidbody movement from Update() */
    transform.Translate( movement * moveSpeed * Time.deltaTime );
    /* apply rigidbody rotation from Update() */
    transform.localRotation = Quaternion.AngleAxis(mouseLook.x, transform.up);
    /* apply camera rotation from Update() */
    Camera.main.transform.localRotation = Quaternion.AngleAxis(-mouseLook.y, Vector3.right);

}

rigidbody.MovePosition(movement * speed * Time.deltaTime)

void FixedUpdate() {
    /* move the rigidbody */
    rigidbody.MovePosition(movement * moveSpeed * Time.deltaTime);
    /* rotate the camera */
    camera.transform.localRotation = Quaternion.AngleAxis(-mouseLook.y, Vector3.right);

    /* but how can i rotate the rigidbody based on the cameras rotation??? */
    rigidbody.MoveRotation(?????);

}