Plugin language always shows WP site language, not profile language

I wrote a plugin that I translated from English to German.
The German translation only shows up, when I change the site’s language to german. Once the site language is set to German, it will always show german. No matter whether I changed my profile language to English or not.
And vice versa – when I set my site language to english, it will always show the English version of the plugin.
All other plugins follow the profile language and show the correct language as expected.
I looked at a ton of other plugins and followed the translation guidelines to the t. I don’t know where the error lies and desperately need some help with this (probably rookie) error.
Thank you guys so much in advance!