How to reset the News app?

Hi. I’m running NC24.0.6 and it works like charm. However I’m using the news app. There are a lot >400 of ATOM sources in it. Sadly I removed some I still would like to use. While I try to add them back I only get the message that they already exist. But they do not.

So I tried to remove some more and to add them back, but it’s the same. I also tried to import my backup OPML file with the same problem.

So I want to reset the app in complete, but uninstallation and reinstallation wont do it and now I’m basically stuck and don’t know how to do it.