I'm an Iranian producer based in Singapore. So basically my mother language is Persian and my daily using language is English. But interestingly, since I moved to Singapore I am producing mostly Chinese songs! Of course I still do work with my Iranian musician friends back in Iran and making Persian songs with them as well as the English language artistes in Singapore, but I realized it is strange for a lot of people that how come I am producing and even composing Chinese songs while I can't speak Chinese more than few daily-use words!
Well, that's my superpower I think! Haha but beside jokes, the language is not a matter in music world. The language only defines the "words" of the song and it doesn't affect the production process. Yes it makes it a bit harder specially in electronic music that as producer I need to play with the pitch or emphasis certain words of lyrics but in overall it's not a matter. And it even gets easier after a while and after a few projects. After more that 6 years living in South East Asia and learning the culture here, now I might not understand the language but I can understand where in the lyrics need to be emphasized...
But as a whole, music is a language itself and the artistes and I communicate through the language of music. We don't limit ourselves to the words. Of course not to mention, some of the awesome Chinese lyricist I work with, usually they put extra effort in their writing and the give me full translation of each line of the lyrics they write and that makes it super convince for me to deal with the song.
But the bottom line is, I do the composition and arrangement, then the lyricist write the Chinese words on the melody and usually gives me the translation, so when the artiste is recording I am totally aware of what mood and feel they must sing with and this make it so beautiful to work with people from different culture.
In fact this cultural differences mostly help our work process instead of stopping it, as we all bring in different elements from our culture and the songs become something really beyond boarders.