Personally, I don't find it helpful enough for me to learn any languages, & frankly, I just use it to make friends, and wander around to kill time. Italki is actually a place where people talk about foreign languages, but there's an overflow of boring & rubbish topics which are good for nothing. & I believe that, everybody has to rely on his/her own efforts to fulfill his/her dream of being a bilingual, trilingual, or even multilingual speaker. & The best method is to get hold of some authoritative and reliable textbooks, dictionaries, & grammar books. It would be of little help to learn a foreign language only by practising oral English or slang words, of course, even if colloquial English is very useful, the basic skill for foreign languages is quite necessary, & I'm sure that you'll benefit from your steady level gradually.