18 year old boy looking for accommondation in Berlin

I am looking for a small apartment or a room to rent for 1 year in Berlin. I received my High School Certificate but I also want to sit for the SAT and ACT tests in order to sent my applications to  the USA Educational Institutions (Universities or Colleges). While staying in Berlin I am going to study for the SAT, register for the test and  find a job. In my school from the 1st grade we were taught German. I have also pass the B1 German Diploma (a diploma that confirms that the individual can live in German and communicate with native speakers).