They look suspicious. Notice which screen you are on. Based on “click next” you seem to be on the Backup Destination screen trying to WebDAV to NextCloud. I’d think you want Hetzner, correct?
You will have to ask the NextCloud people how to backup NextCloud. There’s a help forum like ours.
Duplicati screen 3 Source Data is what you have to work with. I hope you can get to what you need.
If I recall correctly, there’s a database, in addition to files kept in various places. Restore may require special procedures done in the right order. You have a complex application, and need special advice.
Duplicati backs up the files you tell it to back up, and restores per your directions. The rest is your job. Backing up and restoring using a file-oriented backup should be a familiar question to NextCloud help. Presumably there is a way. Actually, my first try at Google found the manual on it. Try reading up near
Backup (and Restoring backup is right below). For NextCloud questions beyond those, try their forum.
For Hetzner questions, maybe they can help. For questions on Duplicati itself, those are handled here.
Returning to your two factor authentication question, I don’t think Duplicati WebDAV can do that, and if you’ve got that at Hetzner, WebDAV might not work, and I have concerns about other protocol options.