Documentation Translations Help
This document will help you in common topics about documentation translations.
No, changing the language on the developer site will not affect the language setting in your personal account.
This means you can have a different language settings for Facebook for iOS, www.facebook.com, and so forth.
Guides for these sections are translated into 16 languages:
All reference documentation is untranslated at this time.
Besides English, no, you can't. At this time all bugs need to be filed in English.