Enemy gameObject didn't move

I'm actually working on a game project with Unity3D in C#. I already have a good part of my project, but i'm confronted at a problem with the implementation of enemies. Firstly I'm following this tutorial. So I have a gameobject for enemy with box collider and basically all I need. And there is my script :

 using UnityEngine;
 using System.Collections;
 
 public class Enemy : MonoBehaviour {
 
 [SerializeField]
 private float rotationSpeed = 180; // In degrees per second
 
 [SerializeField]
 private float movementSpeed = 1f; // In units per second
 
 [SerializeField]
 private float meshRadius = 1f; // In units
 
 private IEnumerator turnTowardsPlayerCoroutine;
 private IEnumerator moveTowardsPlayerCoroutine;
 
 void OnTriggerEnter(Collider collider)
 {
     if (collider.gameObject.tag == "Player")
     {
         float playerDistance = Vector3.Distance(collider.transform.position, transform.position);
 
         // Ignore trigger events from the inner colliders
         if (playerDistance >= 2f * meshRadius)
         {
             turnTowardsPlayerCoroutine = TurnTowardsPlayer(collider.transform);
             moveTowardsPlayerCoroutine = MoveTowardsPlayer(collider.transform);
             StartCoroutine(turnTowardsPlayerCoroutine);
             StartCoroutine(moveTowardsPlayerCoroutine);
         }
     }
 }
 
 void OnTriggerExit(Collider collider)
 {
     if (collider.tag == "Player")
     {
         float playerDistance = Vector3.Distance(collider.transform.position, transform.position);
 
         // Ignore trigger events from the inner colliders
         if (playerDistance >= 2f * meshRadius)
         {
             StopCoroutine(turnTowardsPlayerCoroutine);
             StopCoroutine(moveTowardsPlayerCoroutine);
         }
     }
 }
 
 private IEnumerator TurnTowardsPlayer(Transform player)
 {
     while (true)
     {
         Quaternion targetRotation = Quaternion.LookRotation(player.position - transform.position, Vector3.up);
         targetRotation.x = 0f;
         targetRotation.z = 0f;
 
         transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, rotationSpeed * Time.deltaTime);
         yield return 0;
     }
 }
 
 private IEnumerator MoveTowardsPlayer(Transform player)
 {
     while (true)
     {
         Vector3 playerDirection = transform.position - player.position;
         playerDirection.y = 0;
         playerDirection = playerDirection.normalized;
 
         Vector3 deltaMovement = playerDirection * movementSpeed * Time.deltaTime;
 
         int layermask = LayerMask.GetMask("Environment");
         Vector3 movingTowards = transform.position - playerDirection*meshRadius + (new Vector3(0f, 0.1f, 0f));
         if (Physics.Raycast(movingTowards, Vector3.down, 0.25f, layermask))
         {
             transform.position -= deltaMovement;
         }
 
         yield return 0;
     }
 }
 }

The result is, when I enter in the zone where enemy must attacking me, the enemy rotated towards me but he didn't move. Did I forget something or did something wrong ?

Thanks per advance!

PokeRwOw