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I completely agree that there is a huge gap between B2 and that level you describe as automatic. I'm currently trying to bridge that gap, but I can't live in France so I think it will take me years. I know people who have done it without immersion, so I know it's possible. My solution is to "immerse" myself at home. I do 90% of my reading in French. 90% of the podcasts I listen to are in French. I watch French TV sho…
Author here. I definitely don't feel completely automatic in French, but when having casual conversation I can be fairly automatic if the subject matter isn't too demanding. I think you're absolutely right that without being immersed in French, you will struggle being automatic, especially in all those situations that you only encounter while being in person with actual French speakers. I think getting C1/C2 certific…
Like most skills, language proficiency work in steps, and you are usually only able to see the next step, the rest goes above your head.
In the case of language, the first step is learning the words and grammar. This can be tested. But there is a whole world beyond that. I realized it when talking about the Japanese language with a girl she didn't even talk about things that come up in tests, like vocabulary. Instead she talked about how to talk to different kind of people, idiomatic expressions, how to convey emotions, even the quirks of writing text messages. She was on the next level, the part about describing things was already a given, not something worth talking about. There are certainly many things lying beyond that, maybe accent, body language, a point where the distinction between language and culture starts to blur...
An interesting thing is that AFAIK, there are no tests that evaluate the proper use of "bad" language. French (my native language) is famous for its colorful swearing. And you can't really call yourself fluent if you don't know how to do it. Proper use of casual and even offensive language, is, I think, an important skill that most foreigners lack, in any language, and yet, most test don't go below business level speech.