How to make a motorbike turning mechanism? Here is my current movement script that has a very bad turning mechanism.

 using System.Collections;
  using System.Collections.Generic;
  using UnityEngine;
  
  public class liikkuu : MonoBehaviour
  {
      Rigidbody m_Rigidbody;
      float m_Speed;
  
      public float MinSpeed;
      public float MaxSpeed;
      public float accelerationSpeed;
      float CurrentSpeed;
  
      void Start()
      {
          //Fetch the Rigidbody component you attach from your GameObject
          m_Rigidbody = GetComponent<Rigidbody>();
          //Set the speed of the GameObject
          m_Speed = 30.0f;
      }
  
      void Update()
      {
          if (Input.GetKeyDown(KeyCode.W))  // on key W down set current speed to minimum speed
          {
              CurrentSpeed = MinSpeed;
          }
          if (Input.GetKey(KeyCode.W)) // accelerate while holding the key
          {
              CurrentSpeed += accelerationSpeed;
              m_Rigidbody.velocity = transform.forward * CurrentSpeed;
          }
          if (Input.GetKeyUp(KeyCode.W))  // on key W up reset current speed to minimum speed
          {
              CurrentSpeed = MinSpeed;
          }
  
  
          if (Input.GetKey(KeyCode.D)) // Here is the turning code
          {
  
              transform.Rotate(0, 1.2f, 0);
          }
  
  
          if (Input.GetKey(KeyCode.A))  // Here is the turning code
          {
  
              transform.Rotate(0, -1.2f, 0);
          }
  
      }
  }