Touch Controls for mobile

Hello. I tried in many ways to make touch control for android. But nothing worked. Control of the keyboard works perfectly ... can someone help me? A good tutorial? Or any advice for this script?

This is my script :

 using UnityEngine;
 using System.Collections;
 
 public class Player : MonoBehaviour {
     
     
     private bool _isFacingRight;
     private CharacterController2D _controller;
     private float _normalizedHorizontalSpeed;
     
     public float MaxSpeed = 8;
     public float SpeedAccelerationOnGround = 10f;
     public float SpeedAccelerationInAir = 5f; 
     
     public bool IsDead { get; private set; }
     
     
     public void Awake(){
         _controller = GetComponent<CharacterController2D>();
         _isFacingRight = transform.localScale.x > 0;
     }
     
     public void Update()
     {
         if (!IsDead)
             HandleInput();
         
         var movementFactor = _controller.State.IsGrounded ? SpeedAccelerationOnGround : SpeedAccelerationInAir;
                 
         if(IsDead)
             _controller.SetHorizontalForce(0);
         else
             _controller.SetHorizontalForce(Mathf.Lerp(_controller.Velocity.x, _normalizedHorizontalSpeed * MaxSpeed, Time.deltaTime * movementFactor));
     }
     
     public void Kill()
     {
         
         _controller.HandleCollisions = false;
         collider2D.enabled = false;
         IsDead = true;
         
         _controller.SetForce(new Vector2(0, 20));
         
     }
     
     public void RespawnAt(Transform spawnPoint)
     {
         if (!_isFacingRight)
             Flip();
         
         IsDead = false;
         collider2D.enabled = true;
         _controller.HandleCollisions = true;
         
         transform.position = spawnPoint.position;
     }
     
 
         void HandleInput()
     {
         if (Input.GetKey(KeyCode.D))
         {
             _normalizedHorizontalSpeed = 1;
             if (!_isFacingRight)
                 Flip();
         }
         else if (Input.GetKey(KeyCode.A))
         {
             _normalizedHorizontalSpeed = -1;
             if (_isFacingRight)
                 Flip();
         }
         else
         {
             _normalizedHorizontalSpeed = 0;
         }
         
         if (_controller.CanJump && Input.GetKeyDown(KeyCode.Space))
         {
             _controller.Jump();
         }
     }
     
     
     private void Flip()
     {
         transform.localScale = new Vector3(-transform.localScale.x, transform.localScale.y, transform.localScale.z);
         _isFacingRight = transform.localScale.x > 0;
     }
 }