Young researcher looking for temporary accomodation

I am a Brazilian student (26 years old) moving to Aachen to start my PhD at RWTH. I am a physicist and applied mathematician, and my PhD concerns HPC and its application to the study of turbulent flow. You can find a little more information about me and my project at http://www.stimulate-ejd.eu/people/fellows/guilherme
On the personal side, I am a guy that is usually quiet but really enjoys to cook and to have some good company.

I arrive in Aachen this Monday (03/09) and I am looking for a temporary place to start getting my life in order and look for long term accommodation. I am flexible regarding dates and conditions.
My biggest concern is if I can get a Wohnungsgeberbestätigung from the landlord, since I need to register at the Citizen's Office as soon as possible in order to get the remaining documents for my contract.

Best regards,
Guilherme