How to sync data with google account?

Question

Google

I want to implement login through Google account in my application. Found a lot of great tutorials on how to connect etc. But none of the lessons showed how to then save the data of this user to his google account (or somewhere else), and then to get this data from there during authorization and apply it in the application (by filling in the database).
My questions:
1) Where should user data be saved for synchronization?
2) How to get this data when a user logs into his account?
3) How do normal people synchronize between devices?
I now save the data in a SQLite database, I heard about Firebase, but I don’t know what it is at all and it is somehow related to authorization.
In a word, I would like to achieve an understanding of the entire authorization process through google much deeper than, "this is saved somewhere."
PS and I would also like to know how this will affect the privacy policy.

Answer 1

Firebase yes
https://angularfirebase.com/lessons/managing-fireb...
https://stackoverflow.com/questions/38676915/how-t...