I don't speak any foreign languages but the older I get the easier it becomes to pick up languages and decipher them. For instance, a few months back I was watching the latest mission impossible movie, they were in Russia and I saw a writing on the building but I knew immediately what it meant. I tried to teach myself Russian but only for a few *like 6 years ago but then I got bored and found a different hobby. I knew though what those words meant and I couldn't explain it to people around me but I typed in what I thought I meant into a Russian translator and I was right. Also growing up I have always been extremely accurate at hearing any language and knowing what language it is, the dialect, and where that person usually is from. I mean if there was a Russian and a Ukranian speaking in their Slavic dialect I'm good at telling apart the two.
I'm a people analyzer so I just study people constantly 24/7 picking up things from them that I don't know I'm picking up until day, months, or even years later. Ever since learning about cognitive functions I just apply it to everyday situations with people and create theories by predicting a persons movements or behavior. If I'm right then my theory has been confirmed, but I make sure I predict based on all the other predictions that came to be right. Just so I'm tweaking my analysis on the person to be as accurate as possible, if I'm wrong I discard the theory and learn teach myself why my theory was wrong to prevent future mistakes and go about the more accurate way each time. Based off of all of that I noticed functions and language have a correlation, like I said and you proved, an Si user would have a harder time than a Ti user, it's not only ridiculously noticeable logic but it's what I have come to prove based off of my own analysis of people.
For myself, like I said earlier, it's easy for me to pick apart languages, seeing similarities between other languages, other dialects, and how they're structured, most of the time it's an unconscious process but I'll realize it when languages are spoken around me. I'm also good at deciphering languages which I found out during the military. Everything you said just further proves that functions do learn languages differently, some harder than others. If people studied the functions, just read their definitions and apply it to a possibility of people learning languages, they would notice that an Se user would have a harder time than a Ne user in learning a new language.
While in college I will be teaching myself different languages though to prove a point to myself.