there’s a bit of unfortunate history to it. 1.9 updated the app and some users lost notes, for 1.10 there was a migration that rescued unsynced notes - but that lead to duplicate notes letting sync crash for some users, a correction came in 1.11 avoiding the duplicate key issue.
Not sure on what version you started or where you’re at now, it’s best to start a dedicated thread and leave the HOWTO Notes thread to questions on App functionality.
Some rescue techniques are in the thread where a user lost local, unsynced notes on the 1.9 update - Notes have been deleted / Notizen wurden gelöscht