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).
Yes, my mother tongue is English, and I spoke some Spanish before I began immersing in Italian. At one point, I couldn’t stop speaking ItalSpanGlish. Nobody could understand me.