It could be you just worrying and thinking they are treating you that way. Even if they are treating you like this, separate yourself from being concerned about their opinion, and your individuality and power will shine. I don’t relate to you about stuttering less in a second language, because I stutter more in Japanese and tend to feel a bit insecure because I don’t know the language well. But I think that for you, the German language must give you a feeling and personality that you resonate more with than the personality and experiences you have in English. I think you need to insert more positivity into your English speaking personality. And less expectations on yourself. And btw, do your acquaintances speak two languages? If not, then they probably consider you pretty smart for knowing two languages