Students from the European Union, the United States of America, from Norway, Iceland, Liechtenstein, Australia, Israel, Japan, Canada, New Zealand and Switzerland do not need a visa. They only have to apply for a residence permit.
All other foreign students need a student visa for entering Germany.
We recommend you contact the German authorities (embassy or consulate) as soon as possible. A tourist visa IS NOT SUFFICIENT! If you come with only a tourist visa, you may be obliged to go back home to apply for a student visa.