Be sure the english slang and none-common expressions are as difficult for us as the russian ones are for you. It's ok, i think. You should waste a years for mmm "full diving" into foreing culture, and even after that there's no guarantee you'll be "in" language like a native speaker is. Personally me think that it's almost impossible at all ) or you should be a lingvo genius. The reason is you'll never be able to spend so much time for learning language process as a child can (at home, at school, with friends etc.. how long? 10 years? 15 years?)