Hi Tina, I met my first one from Germany 
I have a S8+ and S9+ and haven't that problem, I can edit, add, agree or delete new notes.
I checked opening a new note, text something, copy, save, open newly and add new conttents to the note, saving again and works fine.
Can you take some screenshots and show us?
Next time please, use a correct place to post, here is an underlounge room, usually not for technicals problems as this one, go to Smartphones and post there.
Pleased to meet you
