I too try my best to learn and use colloquialisms. Excessively formal language is very academic, something you learn in a school rather than by actually communicating with other humans. Inability to understand and communicate using informal language and slang marks us as foreigners. Even subtle differences in word choice can sound weird to native speakers.
I test my fluency by attempting to pass off as a native speaker on the internet. If anyone ever suspected I'm not a native speaker, they never told me. I was once unmasked in an old video game though because of a mistake specific to that game and people from my country, a mistake I had internalized since childhood. That was quite shocking to me...
I test my fluency by attempting to pass off as a native speaker on the internet. If anyone ever suspected I'm not a native speaker, they never told me. I was once unmasked in an old video game though because of a mistake specific to that game and people from my country, a mistake I had internalized since childhood. That was quite shocking to me...