[davidzweig]

Professional proficiency could mean almost anything, though. It could require quite a low level of linguistic skill if you are limiting your conversations to a narrow domain, and speaking with a person who also understands the relevant ideas and concepts. In this case you are just 'indicating' some state, as opposed to composing free-form descriptions. 'A word to the wise', so to speak.

There are some very useful language materials produced by the FSI on the net, hosted on this site: https://fsi-languages.yojik.eu/ The French course in particular is very thorough, and the Chinese looks very good too, although I haven't used it yet.

I am making a special audio player for such materials, some info here: http://smallworld.press/