haha I had a friend in high school, his dad worked at a local store as a clerk, but spoke multiple languages in what appeared to be "fluency", but I was young... anyways, he found this book at a yard sale "Russian by pictures", a year later he is throwing around full Russian sentences...

Some people are just magic at learning languages. 2 vs 10 isn’t that much more work. Always seemed wild to me as I struggled with Spanglish.

That's the main place he learned it but he was also interacting with people in Russian constantly which is what people upthread were saying makes the leap from being able to passably read to conversational and then on to fluency.