Looking for a Room (350-400 Eur per Month) Sep 12 to October 18 (included), or Sep 12-30; or Oct 1-18, different combinations are OK

Hi
I am visiting Berlin, visiting private art galleries, working doing Marketing.I fly back to Mexico City Oct 19. I am looking to Rent a room for short term Sep 12 to Oct 18, or any 2 or 3 other combinations: Sep 12-Oct 12, 15, 18; Sep 15-Oct 15; or Oct 1-18; etc... My budget for 1 month is around 350-400 Euros , or a bit more Euros depending on Location, size of room and How many people in total including me in the Flat.
Schoneberg would be my ideal Location, or close by, or on the U1 or U2 lines 2-7 stops from Nollen-dorfplatz... But other locations will be considered. I am an 39 years old (I have lived in Geneva, NYC and Mexico City where I have my flat). Previously in 2014 I lived with 1 roomate in USA and in 2000 with 2 roomates. I speak English, Spanish and French, but sorry no German. I rented a room in Berlin in 2014 and I can provide him as a reference. I am only 1 person, no pets, non smoker, no drugs. It could be a smoking flat but not inside my Bedroom. Please feel free to ask me any questions. Many thanks
Xavier