I want to know about travel from Guilin - Fenghuang - Zhangjiajie - finally arriving in Chongqing

From GL to Fenghuang, you need to take a train for Huaihua first. Then take a bus for Fenghuang. There is only one train from GL to Huaihua, K651/K654 and you need to book the ticket in advance 20 days in advance. Upon reaching Huaihua, you need to go to the local bus station to find a bus for Fenghuang easily.

After visiting Fenghuang ancient town, you can go to the bus station to take bus for ZJJ. Then you can take a bus for Changsha, where you can find both trains as well as flights for Chongqing. (Both of the trains' and flights' schedule and prices can be found on this website.)