Following with the before example...once you have recovered the data for the user from firebase, you can store it in tinyDB and then, you can recover that data whenever and wherever you want in your app:
With StoreValue you are storing the recovered data from firebase into TinyDB.
With GetValue you are recovering the data stored in tinyDB. You can recover this data in other screens (you need to place a tinyDB component on each screen).
Maybe it would be necessary to take a look at this:
FAQ Section: TinyDB - Frequently Asked Questions - MIT App Inventor Community