This is sadly a very common misconception, mostly due to the Nazi propaganda itself. The pre-war designs where mostly retrofitted civilian machines, the best example are the first planes they build. This was due to the restrictions to rearmament. After the war begun, the meth upped shitheads mostly threw material against every problem they faced (more money = less problems = more good). The result were monstrosities that broke down regularly. Another good example for the propaganda of “ze effizint Jerman Enjeniring” is the Autobahn. There was an Autobahn before. Hitler added some small parts and made sure he and his goons are photographed doing it. Boom, Hitler build the Autobahn.