I am familiar with several south asian and european languages. Bengali, my mother tongue, was the only language I spoke with any confidence, till I was 22. Over years I learned to speak English spiced with strong Bengali accent, Hindi made politically correct by gender-insensitive conjugation, French denuded of sujonctif and other monstrosities, and finally Kannada, which only my wife follows.
I have tried to learn Mandarin and unleash it on unsuspecting Chinese. Given the unfortunate results, I let go the idea.