Trip from Vietnam-Busan-Shanghai-Vietnam

Hi, my boss have business trip to these country. he is French. please support me we can make transit visa or not.
Vietnam (HCM )- Busan from 08/07 to 11/07
Busan-Shanghai 11/07
Shanghai-HCM 11/7-13/07
during the time at Shanghai around 3 days do we have to make visa or transit visa and where we can make it? which documents is requires? and during 3 days at Shanghai he can go out the airport or not?
Thank for your feedback