We have 4 days in shanghai how should we spend it and can I do some cooking classes

In my opinion, 4-day trip in the city is too much, so I suggest you spend two days in the city and another two days in Suzhou.
On the first day, you can go to the local Museum and then go to Yuyuan Garden. Then have lunch near that place. After that you can take a taxi to reach Nanjing Road to visit this famous pedestrian street in the city. Then walk to reach the Bund to explore it and take the Huangpu River Cruise to enjoy the river.
2nd day, Jingan Temple, Xujiahui, Xintiandi and Pudong area.
3rd day, you can take the bullet trains for Suzhou to visit local famous gardens (Sisiter Gardens) in the city.
4th day, you can go to Zhouzhuang to have a look of the real water town.
I heard Cooking in the city is a nice cooking class locally and I think you can have a try there.