Unity Arduino VR problem

Hello Guys, I’am making a VR headset with Arduino and a game with unity. I wired my nano to an MPU-6050 gyro-accel sensor and send its values to unity and this tutorial’s code works pretty well on the arduino side. But I have a problem with the unity code here it is:

using UnityEngine;
using System.Collections;
using System;
using System.IO.Ports;
 
 
public class VR_Main : MonoBehaviour {
    public float x;
    public float y;
    public float z;
 
    SerialPort serial = new SerialPort("COM3", 115200);
 
    void Start() {
        serial.Open();
        serial.ReadTimeout = 2000;
    }
    void Update() {
        if (!serial.IsOpen)
            serial.Open();
 
        serial.Write("a");
        float AcX = int.Parse(serial.ReadLine());
        serial.Write("b");
        float AcY = int.Parse(serial.ReadLine());
        serial.Write("c");
        float AcZ = int.Parse(serial.ReadLine());
        serial.Write("d");
        float GyX = int.Parse(serial.ReadLine());
        serial.Write("e");
        float GyY = int.Parse(serial.ReadLine());
        serial.Write("f");
        float GyZ = int.Parse(serial.ReadLine());
 
        x = AcX / 190 * 0.5f;
        y += GyZ / 3000;
        z = AcY / 190 * 0.1f;
 
        transform.localEulerAngles = new Vector3(-x, -y + 180, z);
    }
}

and here is the problem:
When I move my VR it works well.
but when I’am not moving it keeps rotating on the Y axis slowly…
and the problem is in this lines of code:

x = AcX / 190 * 0.5f;
y += GyZ / 3000;
z = AcY / 190 * 0.1f;

as you can see when I’am using my Accelerometer I don’t use the " += " I use " = " but when I use the gyroscope I must use the " += " to move if I remove the “+” it wont rotate on its own but also if I move my head it wont move…
Do you have any idea how to solve this ?
Thanks…

Any help ?