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).
In linguistics this is called “code switching”, and it is extremely common among native bilinguals.
Dialects, too.
Saint Louis Public Radio has a show titled Code Switch which is about discussing racism and derives it’s name from the behavior.