Shanghai > Hongkong > Shanghai > Hamburg (Germany)

Hey! As an exchange student I am currently holding the X2 Visa with single entry. Since my semester abroad is going to an end, I would like to visit Hongkong before I have to go back to Germany. So here my question:

Is it possible to fly from Shanghai to Hongkong, then go back to Shanghai on Jan 15th (72-hours-transit) and then finally fly to Germany (via Dubai) on Jan 16th? I have doubts because I want to enter China twice in very quick succession then...

THANK YOU!