Yes, in German, "The Cortana" must be stopped, not just because of the information Microsoft collects, but because we want Search Windows back in the start bar.
Cut and paste this into DieCortana.reg and then import it with Regedit, or open RegEdit with admin privs and make the change yourself. Then restart your computer if you dare....
Windows Registry Editor Version 5.00Be warned, that Cortana still looks like she is running in your process tree, because the search and index tools have been rebranded to look like Cortana. Don't turn those off.