Hey can I go to shanghai from Hong Kong for 2 days and back with this visa

You mean you will travel like HK-Shanghai-HK, and want to enjoy the free transit in Shanghai, right? If yes, you won’t be eligible for the free transit in Shanghai because you should fly to a third country or region after staying in Shanghai, but you fly back to HK.
If you travel like US-HK-Shanghai-US, you will be eligible for the free transit in Shanghai.