For English it took me from 10 years old to 20 to be able to fool people in online conversations that I might be native. Now at 33 I am still daily picking up n

For English it took me from 10 years old to 20 to be able to fool people in online conversations that I might be native. Now at 33 I am still daily picking up new English idioms and especially cultural background, but finally it is getting rare to encounter unknown words or phrases. I still (rightly IMO) hesitate to say I can speak Japanese, even though I have lived here for 5 years and spent two of those solely studying the language. I encounter an unknown word in almost every sentence. Like someone here commented for German, having to explain so many words or think of synonyms is annoying enough that a conversation switch to English can happen if it is possible. Imagine talking to a speech recognition system that doesn't understand 10% of your sentences. It quickly makes you want to start typing instead.