I like the website. I’ll recommend it to a few friends who lately expressed interest in how I edit photos with Darktable.
A few entry points have a clear disclaimer that the website is not written by darktable developers. Perhaps that disclaimer could be made a little more obvious, maybe in the footer section?
On the other hand, darktable is an open source effort, so one man’s opinion is not by default any more valuable than another’s. I think the website (in German) is fine as it is.