Hello Netzlichter,
I have made over 40 wp/drupal (CMS) sites int he last 2 years,
I make custom themes with responsive system (mobile, tablet etc).
I can correct all the changes in a few days, on my test server.
Contact me when you are ready to send me the files i need
and get started, i will provide you with a direct link
to see the changes, and can provide detail on fixing them
if you do not wish to provide acces data afer job is done.
Regards,
Villy.