Hallo!
The whole thing costs me a lot of time. I installed context with 'UserInterface de' without a real idea what it means. I didn't know if it brings me german messages or an german interface. Then I forgot this setting and used english statements. All worked well, until I wrote a little testfile, without präambel, and tex complains about \chapter{}. It was very strange!
I would forget about the german interface. Some translations are wrong or misspelled, a lot of other no good german. The english one (and the dutch) is much better (and you don't need to translate your code if something doesn't work and you'd like to ask on the list).
I use the english interface anyhow. As I tould, the whole thing was an accident of a beginner.
If you like to get german messages, you must make your formats with "--response=de", that translates most messages of ConTeXt, but not of TeX.
Grüßlis vom Hraban!
Thank you! Gruß, Wolfgang