Hey there Libor_Novotny,
Thanks for reaching out to Apple Support Communities. I understand you’re having some issues recovering your GoodNotes files from your iPad. I’ll be happy to help.
In the picture, it looks like you are looking at the GoodNotes files directly from your iPad, not in a backup. Since GoodNotes only works with iPadOS, iOS, and Mac, you should be able to open these directly from the GoodNotes app on your iPad. If you can’t open the file in the app, the following steps may help:
Force close the GoodNotes app and restart your iPad:
How to force an app to close on your iPhone, iPad, or iPod touch
Restart your iPad
Check for updates to iPadOS and the GoodNotes app:
Update your iPhone, iPad, or iPod touch
Update apps or use automatic downloads
If the issue continues, contact the app developer and see if they have any steps that can help:
How to contact an app developer
I hope this helps.