Looking for at least 6 months living

I'm living in Dortmund now and my life is very good. However, I must finish my master thesis which has made the struggle to wake up early every day more difficult. For that reason I would like to find a place for only three or four months while I do my final effort. From the middle of September until the end of December or the middle of January could be possible too.
About me.... well I'm from Mexico, I love to travel, to cook and to talk about my culture and the rest of the cultures in the world. My life has changed since the last 4 months when I have been working on my project and I have become in a less social person :-S. But anyway I still trying to feel me not so weird and so different as I used to be.