Hello, I need a bit of Flutter/Firestore help.

My son is a middle school math teacher. He asked me to write a web app that would mimic the game Heads Up. Heads Up is a word game that displays a word. Then the players try to give you clues to get you to say the word. Michael thought it would be a great way to review math vocabulary.

I learned Flutter so I could build the app, then I discovered Firebase to host the app. Everything is working but one missing piece. I’d like to use Firestore to save the teacher’s progress through a list of say 100 terms. As it stands if the teacher begins the review on day two, there will be some repeats even with the list randomized, to avoid that I want to save their place by writing the list of un-reviewed terms to Firestore then retrieving the list with a login the next day. User authentication is working so the UID is available. I simply want to write once upon logging-out and read once on logging in. I want to overwrite the previous list (array) rather than add to it. I understand how to set up the database on the Firebase end. I have the Firebase Rules set up, so an authenticated user has write privileges. I just don’t understand the read and write coding on the Flutter end.

I’ve never asked for help before, so this is a first. Usually, I can just look at examples and figure it out, but I’ve been stuck here for a while.