Like I speak English and Portuguese, learning Dutch, and (not doing it for the sake of a primarily English-speaking community) but I will often switch between the two, like saying “Bom dia/Oi” to someone or “Tchau!”
I may also falar assim and I don’t do it to show off, it’s just comfortable pra mim. I will mix in a few português words. (Not exactly like this but YKWIM, maybe).
Hardly ever, but sometimes I find grammatical, syntactical, etc. elements of the other languages subtly bleeding through in my writing and speech. e.g. habitually writing “1.”, “2.”, and “3.” instead of “1st”, “2nd”, “3rd”, even for an English piece.
Maybe it stems from the way I acquired my languages. Code-switching tends to throw off my thought process, especially if I am the one doing it. I’ll have to finish a thought (or an entire chain of thoughts) in one language, and only then will I have an opportunity to switch the language.