very long LAG in my unity game using arduino

im a first time user of unity3d and ive seen a tutorial on a car simulation using arduino and unity . i followed every steps in the tutorial. i even copy and paste the code for the unity . and it's already running but the problem is it has a 30 seconds delay before reading the inputs that my arduino is sending. here are the codes that im using and here is the tutorial that ive been follwing. hope someone could help me. i really dont know what to do. https://www.youtube.com/watch?v=N9RhSa8oMD8&t=414s

arduino code

 int carRotation=0;          //variable to read the values from the potentiometers
 int carSpeed=0;
 
 void setup() {
   Serial.begin(9600);       //start the serial communication
   pinMode(A0,INPUT);        //initialize the potentiometers inputs
   pinMode(A1,INPUT);
 }
 
 void loop() {
   carRotation = analogRead(A0); //read the values of the potentiometers - between 0 and 1023
   carSpeed = analogRead(A1);
   Serial.print(map(carSpeed,0,1023,-100,100)); //scale it to use it with the car speed
   Serial.print(",");
   Serial.println(map(carRotation,0,1023,-100,100)); //scale it for the car rotation
   delay(50);
 }

car user control code

 using System;
 using UnityEngine;
 using UnityStandardAssets.CrossPlatformInput;
 using System.IO.Ports; //Library to read our ardunio data
 using System.Collections;//to use Ienumarator in our code
 
 namespace UnityStandardAssets.Vehicles.Car
 {
     [RequireComponent(typeof (CarController))]
     public class CarUserControl : MonoBehaviour
     {
         private CarController m_Car; // the car controller we want to use
 
   SerialPort seri = new SerialPort("COM6",9600);//define our port
         private void Awake()
         {
             // get the car controller
    seri.Open();//open our port
    StartCoroutine(ReadDataFromSerialPort());//start loop
             m_Car = GetComponent<CarController>();
          
   }
 
   IEnumerator ReadDataFromSerialPort(){
    while(true){//loop
    string[] values = seri.ReadLine ().Split (',');//we split our string value by , because we write string as carspeed,cartotation in our ardunio codes
    v = (float.Parse(values[0])) / 100;
    h = (float.Parse (values [1])) / 100;
    yield return new WaitForSeconds (.05f);//waiting seconds to read data. It should be same as ardunio code loop delay
    }
   }
 
 
 
   float h;//horizontal (car direction)
   float v;//vertical (car speed)
         private void FixedUpdate()
         {
             // pass the input to the car!
    //Close old codes which created by unity team
             //float h = CrossPlatformInputManager.GetAxis("Horizontal");
             //float v = CrossPlatformInputManager.GetAxis("Vertical");
 #if !MOBILE_INPUT
             float handbrake = CrossPlatformInputManager.GetAxis("Jump");
             m_Car.Move(h, v, v, handbrake);
 #else
             m_Car.Move(h, v, v, 0f);
 #endif
         }
     }
 }