Buhata writes to your device first and syncs afterwards. That is the opposite of most apps, and it is the reason it keeps working in a basement car park.
Working with no connection
Everything functions: adding entries, ticking tasks, the calendar, the lists. Nothing waits on a request.
When a connection returns, changes go up on their own. The dot at the bottom of the sidebar tells you where things stand, and it says a time when it last succeeded.
What if I used it before signing in?
That work belongs to you, so signing in brings it with you rather than replacing it. Anything you created on the device is carried up into the account.
Where both have a record of the same thing, the account's version wins. Nothing you wrote is quietly overwritten by a device holding an older copy.
Two devices, two answers
The account is the source of truth. A device that has been offline takes its copy from the account when it reconnects, and anything it created that the account has never seen is carried up.
Moving to a new phone
Install Buhata, sign in, and wait for the sync dot to show a time. That is all. Nothing needs exporting first.
If the old phone still has things it never managed to send, open it once with a connection before wiping it.
When something looks wrong
If the dot never settles, sign out and back in on the device that seems behind. It will take a fresh copy from the account.