Yes, I think it is possible, but you have to almost pretend to live in that country -- while living where you are. For example: change your phone's language to English/Korean, only listen to music in those languages, watch or listen to the news mostly only in those languages, only read in those languages...and talk a lot, both to others and to yourself in those languages. Almost put yourself mentally and linguistically in the places where those languages are spoken. I know of people who have done that (total emersion at home) and they have become VERY good at their target language. Fluency is a subjective thing. It always depends on many factors if you can speak without hesitation and with (mostly) correct grammar. I can speak fluently about what I ate for breakfast in Italian, but not about the problems following earthquakes in rural Italy. It all depends on your goals.

Yes, it is. Get language partners to practice the target language with, and read as much as you can.

i want to improve my english