Exchange student A&M Texas University...apartment or shared flat for two

I'm Paul 22, I'm looking for myself and my sister Ariana 20, a student apartment on campus or a shared flat (german: WG) with a maximum rent of 350 € each person.

I am a mechanical engineering student at Texas A&M University in Master's degree program and i am taking part in an exchange program that has brought me to RWTH Aachen University. I will study here until end of summer-semester 2018 -respectively october, before returning to the US to finish study.
My sister Ariana is a undergraduate student in medicine and biomedical sciences in the second year. She will complete a eight-month internship at the University of Aachen starting in February, probably until October. Both of us are cosmopolitan people and very liberal and expect our fellow human beings to be open to us as well..

Currently I live in a shared flat with two nice roommates, but due to the fact that soon my sister comes to Germany, I'm looking for an apartment on campus for both of us or a shared flat (WG) with a maximum of one or two people. We prefer residing on campus. I can move out of my current apartment at any time.

fast facts:
-apartment for two, on campus
-or shared flat with max two roommates
-December/ Januar 2018 - at least October 2018

Don't hesitate to contact me. i will respond as soon as possible.