— Thanks a lot! With what little I know of programming I was able to obtain the data and display it on the screen (in a very precarious way). I know that it is not the best way to do it but it is what I could do with a json and ajax. The best thing would be to be able to obtain the data and put them in an array and be able to position the 10 best scores. If you ever manage to do that please let me know in this post.
Here is the file with firebase data collection: https://www.mediafire.com/file/dv84piw2ixqqu0s/Leaderboar_firebase_Ajax_3.c3p/file