Simplify the following text for a Grade 9 native English-speaking person.
Original: Although Berlin claims currywurst as its invention and `` national dish '' , all over Germany , there are more than 20 different types of currywurst .
Simplified: The 1993 novel Die Entdeckung der Currywurst ( `` The Discovery of the Currywurst '' ) by Uwe Timm was made into a 2008 film of the same name . The plot is based on an alternative but unproven theory that currywurst was invented in Hamburg .