The master’s programme does not offer itself preparation classes for german. But the Humboldt-Universität zu Berlin offers courses as “German as a Foreign Language” in the Language centre. These courses are booked out very quickly.
There are several possibilities outside the university, for example Goethe Institut here, which is much more expensive than in most other countries. Volkshochschulen offer a cheaper way. And of course there are a lot of private schools which offer german courses.