I think it may be something to do with the tag, maybe I need to change it since my firebase is different?
I attempted to load your aia project, but it offered me an infinite loop on startup. I removed everything from Initialise, but still got the loop. Removed a few more things and got a "stable" start up, but any attempt to access Firebase presented an error. Lots of issues in your app methinks.
What loop? It runs fine for me, only it starts in the menu screen cause i forgot to switch it back. Did you find the issue with the leaderboard tho?
As I said, I could not get Firebase to respond at all.
Suggest you simplify, get each of the elements working, then put them together. Good app planning 
Eh, thanks. I'll try and do that but I guess its another app put to trash because I dont know how to work with firebase. Btw is there any good tutorial videos on it?
This is why I suggest you set yourself up a new project and try one thing at a time:
"I do, I understand"
Once you get your head around setting the project bucket to a specific "node" in order to get at the tags/data below that level, it will all start to make sense, along with understanding why you need to reset after each operation.
Blindly following video tutorials and using code by others will not develop your understanding.
"Practice makes perfect"