Whichever language I use more, the stuttering seems to be less. I spoke English most of my childhood but now I live in Mongolia. My stuttering was worse when I started to speak Mongolian daily, but it has gotten better. Now, when I speak English, I stutter more. I also speak Korean and I can’t even form a complete sentence without falling into a pitfall in that language. Maybe it has more to do with confidence in the mastery of the language.