Perhaps you should try some spelling variations:
passiver » passive, passiven, passively
passiveren » passiveen, passivenen, passivelyen, passivieren, passieren, passiverer
passiverwerb » passivewerb, passivenwerb, passivelywerb, passiverer
passivene » passiven, passiveand, passiverer

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((passiver OR (passion OR passiveren)) OR (passivene OR passiverwerb)).
• Adding a wildcard symbol may retrieve word variants: ((passiver or (passion or passiveren)) or (passivene or passiverwerb))*.