Move player to left and right ( android Touche )

this script its for windows keyboard i want switch to android touche

using System.Collections; using System.Collections.Generic; using UnityEngine;

 public class PlayerController: MonoBehaviour
 {
 
 public float horizontalInput  ;   
 public float  speed = 10.0f; 
 public GameObject character;
 public GameObject projectilePrefab;
 // Start is called before the first frame update
     void Start()
     {
     
 
     }
 
     // Update is called once per frame
     void Update()
     {
      if(transform.position.x < -20)
       { 
       transform.position = new Vector3(-20, transform.position.y , transform .position.z );
       }
 
 
      else if (transform.position.x > 20)
       { 
 
             transform.position = new Vector3(20.0f, transform.position.y, transform.position.z);
     }
         horizontalInput =  Input.GetAxis("Horizontal");
             transform.Translate(Vector3.right * horizontalInput * Time.deltaTime * speed);
 
 
             if (Input.GetKeyDown(KeyCode.Space))
             {
             Instantiate(projectilePrefab, transform.position, projectilePrefab.transform.rotation);
 
 }   
     }
 }