It totally depends!! If you start living in a foreign country, in few months you will have advance knowledge of their language. Being among speakers, or surrounded by them definitly makes learning language much easier. Why you know your own mother-tongue OR native language very well? because that is what you always heard from your parents, brothers-sisters, or near relatives. Grammar didn't really mattered here, isn't? Practice is the key, and with advent of internet, practicing is not at all that difficult.