I really like to go shopping in this place, even though it's a bit expensive, but at least all organic!
You have a very big choice of vegan and vegetarian products. They are signed as "vegan" on a green sign next to the price. They have many different tofu options and many soy yogurts in different flavors. You can even get a vegan pepperoni pizza and vegan ice cream! The bakery has a vegan breaktime snack "Pausenbrot". If You want to cook Asian they have some good things for it there, too. It's very close to the central station!
Cons: often expensive, no vegan "wilhelmsburger" cheeses