If you want to prolong your stay in Shanghai beyond the expiration of your visa, you should apply for an extension or reissuance three days before the expiration date.

Complete registration on International Services Shanghai.

Log into the website of Government Online-Offline Shanghai.

Choose the service center location where you would like to schedule a visa extension, renewal, or replacement.

Fill in your personal information.

Select the service center, date, and time slot for your reservation.  

You could also schedule a visa extension, renewal and replacement via the WeChat mini-program "Suishenban".

Search "Suishenban", select "出入境专栏”(Entry-Exit Affairs) and then the "Visa/stay permit/residence permit".