It's just a matter on how much time you spend learning the language.
Even if you only consider the time you spent in school merely learning your own native language those school lessons will add up to thousands of hours.
How many adults, who have already "learned" a foreign language, dedicate 6 hours per week purely on further improving their skills in that language for 12 years?
If you are worried about not knowing certain rare words then using a spaced repetition system with a word deck that contains the first 20000 or even 40000 words should help a lot. You will quickly rush through the words you already know. I can do 50 reviews in less than two minutes if I have memorized the words but 50 unknown words will take me at least 20 minutes. At a rate of 30 new words per day you can do 10000 words per year + half a year at the end to make sure every card reaches maturity.
Even if you only consider the time you spent in school merely learning your own native language those school lessons will add up to thousands of hours.
How many adults, who have already "learned" a foreign language, dedicate 6 hours per week purely on further improving their skills in that language for 12 years?
If you are worried about not knowing certain rare words then using a spaced repetition system with a word deck that contains the first 20000 or even 40000 words should help a lot. You will quickly rush through the words you already know. I can do 50 reviews in less than two minutes if I have memorized the words but 50 unknown words will take me at least 20 minutes. At a rate of 30 new words per day you can do 10000 words per year + half a year at the end to make sure every card reaches maturity.