Oh, OK.
I entered the following
dnslookups: Checked and not checked tested
jquerycdn: Only local
proxy»host: proxy.thecompany.de
proxy»port: 80 (Yes, 80 is correct)
proxy-user: myADUsername (ony letters)
proxy»pass: myADPassword (no special chars, only letters and numbers)
proxy»ssl: not checked
proxy»except: field is empty