1 Room flat from July to Octber

Hello! I'm Carolina, I'm 20 years old and I'm from Switzerland. I came from a little city, Lugano, where we speak Italian.
I'm currently in my first year of the State Tourism and Hotel Management School in Switzerland. From July to October I'll be in Berlin for a traineeship in a hotel. I the first month, July, I'll study German in a language school in order to improve my German.
I'm a quiet and tidy person. At the same time I like to know new people and I'm looking forward to living a new experience in Berlin. I've already been in this city, I thing it's awesome, there is plenty of things to do and to discover.
I'm looking for a one room flat in Mitte, Kreuzberg or Schöneberg from July to October. I smoke sometimes but it isn't a problem to live in a no-smoking flat.
As I'll stay only 4 months in Berlin, I would like a furnished flat

Looking forward to hearing from you!
Carolina :)