23 year old portuguese erasmus student and his girlfriend looking for accommodation in Bonn

Me and my girlfriend (both  23 years old),  are looking for the simplest and cheapest room possible. We prefer with private kitchen and Wc but it's not mandatory. We don't smoke or drink alcohol and don't make noise and sleep early. We prefer a room near the university because we do not have a lot of money for transportation.
Our goal is to be able to experience living abroad in the beautiful city of Bonn with very little money. so we need to spend the least possible in our stay in Bonn. If there is any part-time job that we can do, we are happy to take it :)