There are different Business Directories :

Try all different Business Directories offered by
Every Engine has different results,
Most companies are listed in serveral directories
but the results are not the same ...

Products / Produkte
find products
and order them directly (example football, car acessories, beer)

Products via Amazon

Business to Consumers - Companies froviding Products or Sevices for End Users
(example Restaurant)

B2C Directory 11880
B2C Directory Yelp

Business to Business - Companies providing Products for Professionals
(example Manufacturer of Kitchens)
B2C Directort WLW

search in another country
Phone Book of the
maybe the person you are looking for has moved
and can be cound through the directory of another country

search through the government
Germany Gov Search
this search engine goes through
all the German ministeries,
maybe the person you are looking for
has been mentioned at some point.

good luck ...