선생님들은 저 한국어 공부하는걸 알고 있어요 "The other teachers know I am studying Korean." (다른 선생님들은 제가 한국어 공부 하는 걸 알고 있어요.) Makes sense to me.

I understand it but you have to put 제가 or 내가 instead of 저 or 나 when you say you are doing something.. Aw I was trying to look up what these grammatical words are called in English to explain more but I couldn't find it.. I'll comment again when I find.