what's the difference between these sentences?
한국어를 공부하는 최선 다하려고 노력하고 있어요.
한국어를 공부하는 것을 최선 다하려고 노력하고 있어요.
한국어를 공부하는데 최선 다하려고 노력하고 있어요.
I don't know if the first two are correct this way. it's only I remember using the third one.
I would especially like to know what the 데 added to 공부하는 means.
thanks in advance.I think I forgot the (을) particle after 최선, but hope it's still clear ^^'