When you're a foreigner learning a language your experience is mostly from reading. There are words, however, that are much more common at home and in spoken language. So you'll probably never learn the words that a 10 year old kid knows.

One subtle issue in learning words from reading is that with languages like English where there's ambiguity in how to pronounce a given spelling, sometimes you might not guess the correct pronunciation for words you learned. This isn't specific to learning non-native languages either; growing up I read a lot and learned most of my advanced vocabulary that way, so as a teenager I would often find out that I didn't pronounce a word correctly because I had only ever seen it written down before.

I started learning english around 1984, when I began to learn programming. Back then most books were, by very far, in english. I also spent some time in the US (about one year altogether).

Copying lyrics from my favorite songs of the 80s was helpful. And then later on TV series and movies in english.

I've watched Friends, HIMYM and Californication* more than once (it's probably the reason I swear so much) and those really helped.

Now I raised my kid in english: from the beginning she was only ever allowed to watch TV shows in english. And she's always been to international schools, in english too.

The other day she taught me a simply word which, surprisingly enough, I didn't know: a "coaster" (a drink coaster).

My absolute favorite is when she uses english grammar and applies it to french: the rules about where adjectives do go vary between french and english and she regularly messes it up in french (supposedly her "native" language but at this point I wonder whether english ain't a first language, and french second).

And one thing she has that I'll never have is a beautiful, proper, english accent. Mine shall forever be a strong french one.

It is changing. A bulk of learners now get their vocabularies from youtube, netflix and podcasts. Watching kids shows is common recommendation (I disagree with it somewhat, but that does not make it not common), so I think people will learn also those 10 years old world words.