In principle, we have already answered the above, but I’ll add on my own that there is no point in just reading the dictionary of your native language or foreign sense, you need to read new words in context, then the brain will be easy to perceive and remember
The answer is simple - read. After all, reading is the main source of new information and, accordingly, new words. Read slowly and thoughtfully, and ideally also out loud, then new words will settle in your memory, which you can later use in your speech.
There are new words - use the dictionary. But do not just look at the meanings of the words in it and then close it, because it is so very difficult to remember and then apply these words. There is one effective way. You need to take cards, on one side you write the word you want to remember, on the other - its meaning, synonyms and examples of use.
Further, after reading the text, you can make a presentation, this helps to significantly expand your active vocabulary ... Presentations are suitable for a situation where you have read a text in which you come across a lot of unfamiliar words. Retell this text briefly or spoken using these words, and they will remain in your memory.
And, of course, communicating is the easiest way to significantly increase your vocabulary, as well as practice new the words. The more communication, the better.
Just take and read, just not a dictionary, but many, many books. Start with Russian classics, at least the one that was in school. And even if you have read it, it will be useful to reread - firstly, the perception of many things changes with age, and secondly, at school there was not always enough time to comprehend what was read, it was necessary to read there "for show".
Read, communicate with people who read a lot, learn foreign languages. This is unlikely to happen quickly, but the vocabulary will definitely increase.
I have almost no appetite, I melt before our eyes. And I used to gain 75kg freely, it was normal, with an increase of 175.