[NTG-context] Use of marking

HI folks, yesterday while reading along I learned how to suppress the chapter numbers in sections. That was something I was looking for myself. But how do you use marking correctly in startsection? I would like to see "1. Kapitel - 1. Aufgabe" in the header on the right. How can I automate this with marking? And how can I reduce the space between the number (1.) and the title (Kapitel or Aufgabe)? Thanks for your help Thomas