German is a pretty rich language. Depending on how and what you count, there are about 500,000 words . . . though others place it at 1 million or even 5 million. Like I said, it depends on the counting.
English is less complex but still hefty. Call it 600,000 words with room to the upside just depending.
Japanese is in the 240,000 to 500,000 range.
Soooooo . . .
How many of those words do you need to know to have a conversation? How about the number required to be fluent? How about a native speaker?
Obviously, the answers are wildly subjective, but in all cases, it’s in the range of . . .
1,000 – 1,500 words to have a conversation
3,000 – 10,000 to be fluent
25,000+ are what native speakers can use, though I’m betting most don’t use nearly that many (notice the 80/20 distribution?)
Soooo . . .
A small fraction of the total universe, learned in the right order and combinations, gets you in the game, and a slightly bigger fraction puts you in rare air.
It’s true about language. It’s true about everything else.
For the things you need to do really well, it’s worth asking, “What are the critical 1000 words?”