Wow, Mandarin, Serbian, and English as a first language. I do admire it. I struggled with course work in French through high school, even audited the last semester after I'd taken it for credit, and did the proficiency into the last semester for college; I could read a novel in a night, once I got the vocabulary going, but I still can't conduct a rudimentary conversation, and never could. My Dutch brother-in-law speaks maybe six languages, and probably four with full command. Growing up in Europe you get exposure, but I admit, I have minimal aptitude. Apparently. I think people find ways to use language skills, other than teaching, in other careers, that can be really beneficial.