There are some good resturant that serve Indian and pakistani food. Either you have very expensive or the very normal variety of food.
I have not seen a resturant specialising in Bengali food, mostly you get South Indian or North Indian.
You will get nice fish dishes and you can but tinned Rosagoolas if you want.
Normally, for a cheap and decent meal, you can go to Malaaj resturant but take opinion of some ladies be4 coming here