Most local language schools now offer online courses in addition to classroom courses.
You can still find these offers under "Language courses in Potsdam" or "Language courses in Berlin". Under "Language courses on the net" you will find a list of providers who only offer online courses.
University of Potsdam
Welcome Center Potsdam
Am Neuen Palais 10, bldg. 8, room 1.11
14469 Potsdam
Tel.: +49 331 977-1382
Fax: +49 331 977-1798
E-Mail: welcome-center@uni-potsdam.de