How can i create nested-menu with c# script?

i want creat nested menu with script but i have some problem.

 List mButton = new List();
 public RectTransform buttonRect;
 public bool open;
 public int buttonDistance ;
 Vector2[] buttonPos;
 float speed = 10.0f;
 float buttonHeight;

 void Start () {

     buttonHeight = buttonRect.rect.height*2.0f;
     mButton = this.GetComponentsInChildren<Button>(true).
                 Where(x => x.gameObject.transform.parent != transform.parent).ToList();

     buttonPos = new Vector2[mButton.Count];

     this.GetComponent<Button>().onClick.AddListener( () => { OpenMenu();} );

     this.GetComponent<RectTransform>().pivot = new Vector2(1f, 1f);

     foreach (Button b in mButton)
     {
         b.gameObject.SetActive(false);
     }
 }

 public void OpenMenu()
 {
     open = !open;

     for(int i =0;i<mButton.Count;i++)
     {
         if(open)
         {
  
             float xpos = buttonRect.rect.width*1.5f;
            
             float ypos = (i+1)*buttonHeight;

             buttonPos[i] = new Vector2(this.transform.position.x + xpos, this.transform.position.y + ypos);
         }
         else
         {
             buttonPos[i] = this.transform.position;

         }

     }

     StartCoroutine(MoveElements());

 }

 private IEnumerator MoveElements()
 {
     foreach(Button b in mButton)
     {

         b.gameObject.SetActive(true);
     }
     int loops = 0;
     while(loops<= buttonDistance / speed)
     {
         yield return new WaitForSeconds(0.01f);
         for(int i = 0; i < mButton.Count; i++)
         {
             Color c = mButton[i].gameObject.GetComponent<Image>().color;
             if (open)
                 c.a = Mathf.Lerp(c.a, 1, speed * Time.fixedTime);
             else
                 c.a = Mathf.Lerp(c.a, 0, speed * Time.fixedTime);
             mButton[i].gameObject.GetComponent<Image>().color = c;
             mButton[i].gameObject.transform.position = Vector2.Lerp(mButton[i].gameObject.transform.position, buttonPos[i], speed * Time.fixedTime);
         }
         loops++;

     }
     if (!open)
     {
         foreach(Button b in mButton)
         {
             b.gameObject.SetActive(false);
         }
     }
 }