I saw few polyglots' videos on YouTube. These people say, that learning few languages at the same time is more effective, than learning it one by one, that it's even easier. So, I have tried with English, Japanese, Polish and Italian. And surprise! It's too difficult) I have only some level of English, and other languages are too different from each other. It was interesting but hard and it caused a severe headache. Now I learn English and Japanese and sometimes try to read in Polish apart, because this language is a bit like mine (Ukrainian), so I can intuitively understand it.