Okay, it's getting clear that I'm in the wrong here with my insistence that languages don't mix and foreign words can't be inserted mid-sentence, yet that is my experience as well as behaviors of people sharing the language, incidentally including GP who suggested that I can always do the switching dance - people can if wanted, but normally don't. It's considered a show-off if the inserted word could be understood at all.

Perhaps I have to admit that my particular primary language is officially a human equivalent of an esoteric language; the myth that it's a complex language is increasingly becoming obsolete(for good!), but maybe it still qualify as being esoteric one that are not insignificantly more incompatible with others.