The most basic vocabulary in the English language is about 800 word families. If you know merely these words, you can already understand up to 75% of a language as it is spoken in normal life.
At the next level, to understand dialogue in a film or TV, you’ll need about 3000 word families. To read novels, newspapers and articles, you need about 8000 words.
Finally, to achieve native proficiency in English, you need to know a staggering 20,000 word families. Besides, all those additional words get more and more obscure.
Skills are easy to become fluent in – just focus on learning the essential parts. However, there is no shortcut to mastery. It is always a long and hard slog.