I am a chinese as well, so I can give some info related to it.
It was heard that Chinese nationalist army did purchase a series of weapons from Germany, including 88mm AA guns, 150mm Horwitzer and noticably the Mauser rilfes and Mauser C96 pistol~~~in Chinese it was nicknamed as "BOX-SIZED CANNONs". A small no of MP28 were purchased by Chinese as well.
The M35 helmets were supplied by Germany, it was heard that Chinese Elite division equipped with M35 helmets even earlier than their German counterpart. Chinese did duplicate the Mauser rifles, C96 pistols, M-35 helmets and many of them.
Undoubtedly, the German-made weapons caused a huge casulty upon the japanese invaders. Japanese gov did repeatedly make a series of protests against Germany for this practice.
Actually many experienced German officers worked as the advisors of Chinese nationalist army from 1920s to 1930s, which was approved by Hilter initially until 1938.