My brain has a very strange way of dealing with languages. It has an "English" switch and a "non-English" switch.
Despite the fact that I know some Spanish and Japanese, my brain enjoys mixing them up. For example, here's one I caught myself thinking.
Vamanos is "let's go," in Spanish.
And in Japanese, "shouka" is a suffix for "shall we?" So for example, ikimashouka would be, "shall we go?"
In my head, I made up "vamanashouka."
I'll also end up tacking "ka" at the end of Spanish words, because in Japanese that would make it a question. This is what I get for switching back and forth between language studies.
If that's not bad enough, I've also been known to pronounce English words wrong if I've recently been studying other languages.
Once I went out to dinner with some people, who at the time were friends. It was a Chinese restaurant, and I wanted to order chow fun. but when I ordered it, I mispronounced it. And everyone at the table jumped on me, exclaiming in disgust that I'd pronounced it wrong. I was so pissed at them. I like chow fun and had never pronounced wrong before. But because I'd been studying Japanese, it just came out wrong. And they all leapt down my throat, making me look like a total loser in front of the server.
I pronounce English words wrong if I've been studying Japanese. Let alone Chinese, which I know only a few words of.
I didn't mean for this to turn into a vent. But if I mess up a language (including English), this may be why.