Monsters frozen when attacking multiple walls

Unity Engine
1

My monsters froze on the place playing the running animation.
I think that the randomly spawned monsters know to attack the walls but IDK why they don’t move, anyone can take a look at my script

Maybe someone knows how to put the closest in the destination = gameObject in the update function

// Keeping up-to-date where player is, so enemy will follow him
    void Update ()
    {       
        //GetComponent<NavMeshAgent> ().destination = GameObject.FindGameObjectsWithTag("wall") = closest;

        // On hit by player weapons
        if (currentHealth <= 0)
        {   
            //transform.Translate = new Vector3 (0, 0, 0);
            //GetComponent<NavMeshAgent> = transform.position;
            GetComponent<Animation>().Play("drop down");
            Destroy(gameObject,0.5f);
            guiDisplay.gold ++;
        }
    }
       
    // Find the name of the closest wall
    GameObject FindClosestWall()
    {
        GameObject[] find; // Creates an array find
        find = GameObject.FindGameObjectsWithTag ("wall"); // Find objects with a tag wall
        GameObject closest = null;
        float distance = Mathf.Infinity;
        Vector3 position = transform.position;

        foreach (GameObject go in find)
        {
            Vector3 diff = go.transform.position - position;
            float curDistance = diff.sqrMagnitude;
            if (curDistance < distance)
            {
                closest = go;
                distance = curDistance;
            }
        }
        return closest;
    }
2

Someone knows how to fuse the return closest value in

GetComponent<NavMeshAgent> = transform.position;