How to get the enemy to walking from one side

And aew guys all right? Good esotu working on a project for a shooter game, wanted to make my enemy to be walking from one side to another, and so see the character begin to follow him and shooting, the part to detect the position of the enemy player is already now the question is do they go from one place to another, and then he sees the player will chase you, but if the player leaves the field of his vision of the enemy to follow him and turn to walk from one side to another. Well follow the code I used to make the enemy detect the position of the player:

using UnityEngine;

 class Enemy : MonoBehaviour
 {
     public GameObject player;
     public float angleRange = 30; //angulo de visao do inimigo 30 = 45 graus
     public float viewRange = 30; // distancia que o inimigo enxerga
     public RaycastHit lastPos;
     public Vector3 dist;

     public int vel = 1;
     public Vector3 dis = Vector3.zero;
     public Transform jogadorPos;
     public Transform saidabala;
     public Rigidbody bala;
     public int timer = 0;
     public int hp = 20;
     public int velTiro = 500;


     public void Update()
     {
         dis = jogadorPos.position - transform.position; //Determina a direção do Ray lançado como sempre em direção ao Player

         if (Vector3.Angle(dis, transform.forward) < angleRange) // Testa se o Player está dentro do ângulo de visão determinado
         {
             if (Physics.Raycast(transform.position, dis, out lastPos, viewRange))
             {
                 if (lastPos.collider.tag == "Player")   // se o inimigo enxergar o jogador
                 {
                     Attack();
                     timer += 1;
                 }

             }
         }

         if (timer > 60)
         {
             Rigidbody b = GameObject.Instantiate(bala, saidabala.position, saidabala.rotation) as Rigidbody;
             b.AddForce(velTiro * b.transform.forward);
             timer = 0;
         }
         if (hp <= 0)
         {
             GameObject.Destroy(gameObject);
         }
     }

     public void Attack()
     {
         transform.LookAt(lastPos.transform.position);
         dist = transform.position - lastPos.transform.position;
         if (dist.magnitude > 3)
         {
             transform.position = Vector3.MoveTowards(transform.position, lastPos.transform.position, Time.deltaTime * 3);

         }
     }

     public void OnCollisionEnter(Collision hit)
     {
         if (hit.gameObject.tag == "bala")
         {
             hp -= 1;
         }

     }


 }

I thank the help guys hugs.