I want to visit shenzhen for 2 nights and 3 days from Hong Kong.

Hey, this town deserves your time. Here is my suggestion for your stay: one day in Splendid China & Folk Cultural Village, Window of the World; the second day is suggested to spend in Dameisha or Xiaomeisha Scenic Area and then Dongmen Pedestrian Street; on the last day, you can have fun at the Safari Park and Happy Valley.