You might want re-think this sentence; 'I know the Englsih adequately. But I don't have pretty much knowledge in english vocabularies.".

I know English adequately, but I don't have much knowledge of English vocabulary.

Hi Tahia,

You can endorse your language by any ways:

the most common one is "reading". the question is what to read?

first, you can read electronic English newspaper like The Telegraph (http://www.telegraph.co.uk/) or Washington post (https://www.washingtonpost.com/) that will add to your vocab collection regarding public and international issues that happen in the world.

Second, you can follow famous English pages on Facebook, read comments, and recognize how natives express their feelings and opinions in English.

If you find a word that is not familiar, check it on Merriam-Webster (http://www.merriam-webster.com/) 

Another skill is listening. any people can know a lot of words but can't pronounce them in a right way. so my advice is to try this interesting website Voscreen (https://www.voscreen.com/), that helps you improve your English language skills on your own language  through short video clips. More advanced, you should watch English movies with English subtitles below. Popcorn app. Can provide this service for you (http://popcorn-time.to/).

Finally, find a native English partner as much as you can. This will also help a lot. 

I hope these words can make sense with you, 

Good Luck