Help with corutines

I want to make my enemy shoot every 1 second .

using UnityEngine;
using System.Collections;

public class enemyshoot : MonoBehaviour {

public Transform spawnbulletenemy;
public Rigidbody bullet;
public float brzinametka = 5f;

// Use this for initialization
void Start () {
	StartCoroutine (MyCorutine());
}

// Update is called once per frame
void Update () {

	MyCorutine ();

}

IEnumerator MyCorutine()
{
	Rigidbody metakkojileti;
	metakkojileti = Instantiate (bullet, spawnbulletenemy.position, spawnbulletenemy.rotation) as Rigidbody;
	metakkojileti.AddForce (spawnbulletenemy.forward * brzinametka); 

	yield return new WaitForSeconds (1);
}

}

This is my script , problem is that it shoots only 1 bullet and then it dosent anymore .

You gotta loop the contents in your function. Right now it will only spawn a bullet, shoot it and then wait a second and then its done. You want to repeat this process and to do this you need to wrap up your content into a loop.

Is the enemy gonna shoot all the time? No stopping? use while(true):

IEnumerator MyCouroutine()
{
     while(true)
     {
          //your code
     }
}

This way it will loop the content in your couroutine forever, unless the script gets disabled/destroyed.