You're English is great and I could understand everything you wanted to say, but here are my pedantic corrections. 

Foreign Language Learning Process

I'(m)'ve been wondering, how much time does it take to learn a foreign language. How do people even manage to (learn) perfect more than one foreign language which aren't in the same language group (perfectly)? Let's talk about English. To be honest, I have been learning English for about 1.5 years from the very beginning (elementary level) but I'm still far away from perfect knowledge of it in all aspects (reading, writing, listening, and speaking). It took a huge amount of time to get into grammar as English grammar is quite different from Ukrainian('s) and Russian('s ones) (and from Slavonic languages in general). Not sure about others, but its probably (it goes) a bit easier for instance for Poles as the Polish language has a(n) Latin alphabet at least and(,) is at the same time(,) a (belongs to) Slavonic language(s).
Also, the process of learning the English language (learning process) (ac)requires a constantly expanding vocabulary; learning the meanings of phrasal verbs and idioms and ways to use them. Yeah, at the first glance it looks not so hard, but without using the learned materials in practice, they are simply worth nothing. Also it is important to listen to something in the language you are learning. And I think it's much better if the materials you listen to are informal. Formal language is also ok, but informal (one) is widely used.
So, why (I')am I telling you that? I (had been learning) learnt German for about 5 years in school but now I can't even recall which tenses (are) there are, without mentioning the fact that I can't speak German now at all. Why? Because I didn't have any practice in German (since) after I graduated from school. So I mean to say that real life practice and lifelong learning are the most important requirements in successfully learning a foreign language (learning process).
And the last thing I want to say here is that I'm still wondering and it still remains a puzzle for me to understand how people know several languages perfectly at the same time.