Trying to create an endless vertical level

Hi guys, I got to code an app for my school project. I'm trying to learn how to code in C# through following this tutorial: https://www.raywenderlich.com/69544/make-game-like-jetpack-joyride-unity-2d-part-2 . In the tutorial, although a endless level is created, it's horizontal, opposed to what I'm looking for. So I took the code and modified it, that as far as I know, it should work, but it does not. Might be important to know, that the player moves, not the background. Here is my code:

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;

 public class GeneratorScript : MonoBehaviour {
     public GameObject[] availableRooms;

 public List<GameObject> currentRooms;

 private float screenHeightInPoints;
 // Use this for initialization
 void Start () {
     screenHeightInPoints = 2.0f * Camera.main.orthographicSize;
 }
 void GenerateRoomIfRequired()
 {

     List<GameObject> roomsToRemove = new List<GameObject>(); 


     bool addRooms = true;        // will be set false most of the time in the for part


     float playerY = transform.position.y; // getting the players position


     float removeRoomY = playerY - screenHeightInPoints;      // the point a room should be removed (isn't seen by the player);  


     float addRoomY = playerY + screenHeightInPoints;  // the point a room should be added


     float farthestRoomEndY = 0;

     foreach(var room in currentRooms)
     {

         float roomHeight = room.transform.FindChild("bg").localScale.y + room.transform.FindChild("bf_window").localScale.y; // setting the room height by adding the heigth of both parts of the room
         float roomStartY = room.transform.position.y - (roomHeight * 0.5f);    //setting the start of a room
         float roomEndY = roomStartY + roomHeight;    //setting the end of a room                        


         if (roomStartY > addRoomY)
             addRooms = false; // no room should be added


         if (roomEndY < removeRoomY)
             roomsToRemove.Add(room); // room should be deleted


         farthestRoomEndY = Mathf.Max(farthestRoomEndY, roomEndY); // setting the end of the room
     }


     foreach(var room in roomsToRemove)
     {
         currentRooms.Remove(room); //destroying the rooms
         Destroy(room);            
     }


     if (addRooms)
         AddRoom(farthestRoomEndY); //adding the room
 }
 void AddRoom(float farhtestRoomEndY)
 {

     int randomRoomIndex = Random.Range(0, availableRooms.Length); //choosing a random prefab ot of the availableRooms array


     GameObject room = (GameObject)Instantiate(availableRooms[randomRoomIndex]); //creating that prefab


     float roomHeight = room.transform.FindChild("bg").localScale.y + room.transform.FindChild("bg_window").localScale.y; //getting the height of both textures to set the room height


     float roomCenter = farhtestRoomEndY + roomHeight * 0.5f; // setting the center height of the room one wants to add, adding half the room height to the end of the room


     room.transform.position = new Vector3( 0, roomCenter, 0); // moving the new room on top of the old room


     currentRooms.Add(room); // storing the newly created room in the currentRooms array     
 }


 void FixedUpdate () 
 {    
     GenerateRoomIfRequired();
 }

}

On top, I read that it's better to simply move the rooms instead of destroying and creating them, does someone have an idea or even solution on that? Excuse my English, I'm just a student from Germany. Thanks in advance.