I think this was my problem! I still don’t know how to use nodes. I was skimming through other examples and I realized that my json structure is a bit different from the ones people usually have. I am really making a confusion.
I made 2 different databases and they look just the same (except for the ID I added to the second):
Database 1: https://myvocab-30705.firebaseio.com/.json
Database 2: https://vocab2-2353a.firebaseio.com/.json
When I look at the JSON file, there I find the difference:
Database 1: {“0”:{“Alemao”:“Guten Morgen”,“Box”:0,“Data”:"",“Nivel”:“A1”,“Portugues”:“bom dia”,“aux”:""},…}
Database 2: [{“Alemao”:“Guten Morgen”,“Box”:0,“Data”:"",“Nivel”:“A1”,“Portugues”:“bom dia”,“aux”:"",“id”:1},…]
This is the confusion I am making. My JSON was originally written as DATABASE 1, and most of the examples I saw contain a JSON file like DATABASE 2.