I have activated numbering sections by 
*\setuphead[section][number=yes]*, and now the numbers are in the toc, 
too, as they should. How to show the numbers in the header, too?

The header is: *\setupheadertexts 
[][{\grau{\tfx\getmarking[section]}}][{\definedfont[name:myriadprosemibold 
at 10pt]\grau\getmarking[chapter]}][]*

But the numbers of the sections are not shown in the header, only the 
titles.

Thanks!
Huseyin