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;
	}
}

The examples on the Input documentation are pretty useful.