how to load random / shuffle scene without repeating current scene? (when button next level pressed)

hi, im newbie. please help me to solve these problem. (im using unity 2018.4.28f1)

so, i make an android platformer game. i have several scene. the first scene (main menu) has a game button, and when it pressed it will appear a randomized level.

and then, when the player successfully passes the level, there is a screen with "next level" button (the button could randomize next scene)

but, when it pressed. it could be random scene, and could be repeating scene. what i want is, when the scene has been played, the scene can't be repeated again and a random new scene appears until all scene finish. please tell me the full tutorial because im very newbie. thanks in advance! it helps me a lot

so here is my code in a gameobject called RandomScene, the gameobject is part of inspector Button "Next Level" & MainMenu (in inspector: OnClick () -> LoadRandomScene.RandomScene)

 using System.Collections; using System.Collections.Generic; using
 UnityEngine; using
 UnityEngine.SceneManagement;
 
 public class LoadRandomScene :
  MonoBehaviour {
 // Start is called before the first frame update
 public void RandomScene()

 {
          int index = Random.Range(5,9);
          SceneManager.LoadScene(index);
          Debug.Log("Scene Loaded");
      }
  
 }