Again, you are switching languages in the wiki *only* for anything wiki-related e.g. navigation, context menus etc., not for custom content like articles. This is working as intended and is *not* a bug. There is no auto-translate for articles on the wiki. Each article would have to be translated and insert into the wiki on g-portal.com, something that takes a huge amount of time to do. Especially since there is already a perfectly fine wiki on g-portal.us for anyone who needs articles in English.
I do agree though, that there could be a link on the German wiki that links to the English one.