Simplify the following text for a Grade 10 native English-speaking person.
Original: He graduated from the local gymnasium and then served in the military from 1967 to 1971 after which he studied Economics at the University of Bonn , earning his doctorate .
Simplified: He graduated from the local gymnasium and then served in the military from 1967 to 1971 . Then , he studied Economics at the University of Bonn , earning his doctorate .