Since I learned farsi and live with my Iranian wife, I actually can't speak french fluently any more. After 3 days in France, the reverse thing happens and I talk to my wife in French, which she does not understand. Somehow, French and Persian occupy the same area of my brain. I also find that native French/Farsi speakers have a similar (not equal) accent when talking German. I always say " when someone calls and has a French accent, but the name sounds Middle Eastern, he's Iranian"

I had something similar - I learnt a bunch of spanish when I was in high school, then moved to india and learnt a bunch of hindi. And when I tried speaking spanish again after learning all that hindi, I found I couldn't articulate in spanish, only in hindi. I would think of something in spanish, and then out of my mouth would come hindi. It was funny and puzzling at the same time