Camouflage 2: Familiar to Foreign

I had spent a day in a conference held in English. At the evening I was going to have a dinner with German colleagues. I speak fluently these both languages. I was listening to a conversation in German with my tired brain. Suddenly I heard somebody talk a foreign language. I started to listen it more carefully, and wondered what language it might be. After a short moment I understood it was my mother tongue Finnish.