What can I do in Zhangjiajie from Thurs 1.20pm to Sat 11.15am. How best to plan this short time?

Hello, please advise:
I am going to stay near the railway and bus station in Zhangjiajie. I will be free from Thursday 1.20 pm to Saturday 11.15 am (less than 2 days).

1) I would like to visit Tianmen Mountain. Should I go on Friday, and how many hours does this trip take?
2) To go to Tianmen Mountain, is it best to book a tour and is it easy to find a tour place.
3) Where can I visit on Thursday afternoon & the short Saturday morning?

Thank you very much.