For trips outside Freiburg, you have several opportunities to reach those destinations. An official ESN partner is Flixbus, you may already know it - their network from Freiburg reaches many cities, from Milan to Berlin, within a few hours.
The closest airport is Basel/Mulhouse/Freiburg (BSL) where you can go to by the AirportShuttle. Other options are FKB in Baden/Karlsruhe or Stuttgart (STR).
It's also common to travel by blablacar.de, you will find an endless amount of destinations - and you find the best option on busliniensuche.de.