The Centrum is temporary the best spot in Hannover for vegan burgers and other fast food. They offer most of the dishes in vegan. But be careful: Sometimes they come in trouble with that and you get it in vegetarian or with meat. Once it happened to me. I ordered a burger in vegan but I got with meat. But when I complained about it I got a new burger for free. I think that's okay then. :) The other 10 times I went to this restaurant I always got what I'd ordered.
Taste the burgers, especially the Chiliburger is my very favourite! :) Cozy atmosphere, friendly staff.
Cons: You can't pay with cash card, Sometimes trouble with orders