I've run into amazing customer service when I've contacted companies in Germany about stuff. For example, a 1960s vintage pressure cooker (Sikkomat) handed down from my mom. I wrote the manufacturer, asking about how the secondary safety works, and they replied saying regrettably the manual is out of print, but here's a photocopy, enclosed.

So with Bosch, see if you can find a German address/feedback form. Don't worry, they'll understand English.