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).
My wife and I are constantly switching between English and French when conversing amongst ourselves. I’ve often noted that when we want to emphasize a sentence, we use the others native language. It also comes in handy when in public and we want to convey something in secret, because both of our accents in our mother languages are quite strong, so at a whisper even people who know the language but are not fluent will not grasp what we are saying.