Is there way to learn english for english speakers?
I know only english, but poorly. Is there way to practice it using duolingo? Learn new worlds and so on?
Keep reading books. Five books is not a lot. Whenever you find a word that seems important and you don't know its meaning, look it up and learn it. After a while you'll have a much bigger English vocabulary. Also practice writing @ http://lang-8.com/ . Write a few sentences, submit it, and wait for the corrections.
From the way you write I'd say your English is quite good. Duolingo's method is for learning the basics which you have already surpassed in English. Your way to learn English is to practice it: read, listen, watch movies, write, talk.
You can learn the basics in a few months, but achieving real fluency takes years. It is not something you can get by reading the exact number of books. Five books is good, but it's probably too early to notice any big effect. Read for your pleasure, not just for the sake of improving English. After a few years you'll look back and see how much better in English you are. Yes, I said years. If you don't give up your practice, you will learn English for the rest of your life and still the native speakers may be able to tell you are not native.
I am Russian, and English is my second language. I have to admit that learning other languages through English helped me improve my English as well. It was not the sentences I was given to translate that helped, but rather participation in discussions.