Samsung Galaxy notebook no longer works without a power connection after an update, what to do?

So I don't use my Note that often and handle my devices very carefully, so I hardly dropped it or bumped it into a protective bag, etc.

Suddenly I can't start up my Note without it being plugged in. When I check the battery level, it only says 0%, then it goes to 100 and when I remove the power cord, my tablet turns off.

Do not understand why this is and how can I fix it without my data being deleted?

The battery appears to be defective.

But that can't be, everything was still working before the update