My father always said you really know a language when you start to dream in that language. I have never had this experience. I definitely never dreamed in Oshiwambo (though I still slip and throw random words in when I get tired). The closest I probably ever came was the summer I was in Germany and was honestly studying and trying to learn German.
Though I had Bengali lessons. I still don't speak much at all other than to argue with taxi drivers or fruit and veggie-wallas in the market. I know less Bengali than I know Oshiwambo. Though I can understand a fair amount when people are speaking around me and I listen carefully.
Well about a week ago it happened. I had an entire dream in Bengali. The funny thing is, even in my dream I didn't understand it. I just caught the random bits a pieces like I always do. There went Dad's theory.