You might want to start your search at the flugplatz egelsbach homepage:
http://www.egelsbach-airport.com/
A flightschool on the field:
http://www.afc-aeroservice.com/
Or just hit google with "flugschule egelsbach", this should produce some links.
Egelsbach is the GA-Airfield serving Frankfurt.
hth, cheers,
sunnfun