It is recommended to visit Zhangjiajie for about 3-4 days, Tianmen Mountain 1 day, Forest Park for 2-3 days and Grand Canyon 1 day.
You can arrange it this way. The more detailed itinerary needs to be tailored according to your arrival time and return time.
If you are not familiar with the route, you can book an inn, which provides services such as route planning and map giving, and recommend yourself to Mu Zi Youth Hostel to make your free travel more convenient.
I hope my answer can help you. Welcome to the beautiful Zhangjiajie.