Hello,
I am subletting a 1-room apartment in the center of Aachen (Elisenbrunnen). It's all new and renovated. Only for students. It costs 550€, everything included, water, electricity... There is bike storage, elevator, terrace and many common rooms to study and spend time with your friends.
I am subletting an apartment offered by RWTH International Office. More info here:
https://housing-aachen.de/
I say I rent it from April to September, but I could start subletting before.
If you are in Aachen, you can come see it. Or if you want pictures, you can contact me to my email.