27 year old man, looking for accommodation in Aachen

My name is Thodoris, I come from Chania and recently signed a working contract with DWI-Leibniz Institute (in collaboration with RWTH) for 3 years. I will be flying to Aachen on the 29th of November and looking for accommodation. My wife is also flying to Aachen one month after me (January), so, basically, we are looking for an apartment >=40 m2,  furnished (or partly furnished) and up to 600 euro per month rent (including heating, electricity, water and internet). Although, since I haven't found anything yet and I will be in Aachen in 29.11, I am also looking for a short time stay (1 month) alone or with a roomate, until I find a more permanent solution.