The "Studentenwerk" in your region offers zero-interest short term loans to students: http://www.my-stuwe.de/geld/studienkredite-darlehen/kurzfris...

And maybe contact them for local, more personalized advice: http://www.studit.uni-tuebingen.de/english/about-us.php

Good luck and don't give up! ("Studentjahre sind keine Herrenjahre" ;)