Ron G. answered 06/04/19
Multiple levels Math, Science, Writing
My own skills in languages other than English are rudimentary, but I can tell you what I was always taught when studying TESOL: if you want to really learn how people use their own language, hang around with a group of them for a bit. After you start to get comfortable, ask if they can help you practice.
I have known Americans who invite internationals who do as I suggest to dinner. Bonus! :-)