Simplify the following text for a Grade 7 native English-speaking person.
Original: Opel , full name Adam Opel AG , is an automobile maker in Germany , founded in 1862 . Since 1929 , Opel is the german brand of the american automaker General Motors .
Simplified: They sold the Opel Kadett , Opel Corsa , Opel Ascona and Opel Senator .