View report builder in english

Where does the report builder get its language setting from? I have a browser set to English, I have an English operating system - and I'm still getting the thing in German. And actually it's not exactly obvious what people where trying to translate and say all the time so I really need an English version to find stuff - besides we have some English only people at our site and we need to change the language setting for them, otherwise they won't be able to work at all.

unfortunately I couldn't find anything at all about that topic in my search. I hope someone can point me in the right direction. It's quite infuriating really...