Movement

public float speed = 5;
    public float CameraSpeed = 3;
    public GameObject mainCamera;
    private Rigidbody rigidBody;
    private Vector3 movingVectorVertical;
    private Vector3 movingVectorHorizintal;
    // Initialization
    void Start()
    {
        rigidBody = GetComponent<Rigidbody>();
    }
    // Update is called once per frame
    void Update()
    {
        if (Input.GetKey("up") || Input.GetKey("w"))
        {
            movingVectorVertical = transform.forward * speed;
        }
        else if (Input.GetKey("down") || Input.GetKey("s"))
        {
            movingVectorVertical = -transform.forward * speed;
        }
        if (Input.GetKey("right") || Input.GetKey("d"))
        {
            movingVectorHorizintal = transform.right * speed;
        }
        else if (Input.GetKey("left") || Input.GetKey("a"))
        {
            movingVectorHorizintal = -transform.right * speed;
        }
        if (!(Input.GetKey("up") || Input.GetKey("w")) && !(Input.GetKey("down") || Input.GetKey("s")))
        {
            movingVectorVertical = Vector3.zero;
        }
        if (!(Input.GetKey("right") || Input.GetKey("d")) && !(Input.GetKey("left") || Input.GetKey("a")))
        {
            movingVectorHorizintal = Vector3.zero;
        }
        transform.Rotate(0, Input.GetAxis("Mouse X") * CameraSpeed, 0);
    }
    void FixedUpdate()
    {
        var moveVec = movingVectorVertical + movingVectorHorizintal;
        rigidBody.velocity = new Vector3(moveVec.x, 0, moveVec.z);
        rigidBody.rotation = Quaternion.Euler(rigidBody.rotation.eulerAngles + new Vector3(0f, Input.GetAxis("Mouse X") * CameraSpeed, 0f));
        mainCamera.transform.rotation = Quaternion.Euler(mainCamera.transform.rotation.eulerAngles + new Vector3(-CameraSpeed * Input.GetAxis("Mouse Y"), 0f, 0f));
    }