By car:
Highway A5, exit "Offenburg", continue B33 in direction of "Villingen-Schwenningen"
Highway A81, Exit "Villingen-Schwenningen", continue B33 in direction of "Offenburg"

By train:
Route Karlsruhe-Basel
until "Offenburg"-train station (IC and ICE-trains)
(then transfer to bus or regional train to "Gengenbach")