Im making a tour to China and Japan, so I need to think how many days in what places are the best.

I was thinking 3 o 4 days at Beijing, then Xian, 2 or 3 in Shanghai, Chengdu and Hong Kong. I'm not sure about Guilin and Hangzhou.
What do you think? how many days do i need in the places? Do you recommend quit or add some place?
Thank you!