I am a Cdn flying into Shanghai. To stay 72 hrs so I need to do anything? Can the 72 hrs be split?

Cdn citizen, cdn passport. Landing Shanghai overnight , then to Taiwan , back to Shanghai 2 nights and depart for Canada. Also do I need one for 4 days Taiwan? I understood no visa required for Taiwan and 72 hrs free transit but people at work are questioning that. Now I am worried. Travelling alone for quick vacation.
I appreciate your help! Thank you.