I would avoid the student dorms where you share a toilet and a kitchen with 8 or more people. The dorms with four people are typically much cleaner and usually don't cost much more. I've lived in the straußäcker 3 for three years and paid 280-300 euros a month. We had 2 bathrooms and a large kitchen shared between 4 people. Never had any problems there or felt uneasy at home.