Thank you, Nina. Train schedule and time taken ?

Hi again, actually there is absolutely no necessary to stay at Yingtan or Zhuzhou for a night. Here I would provide you with several transfer approaches.
1. At Changsha, you can take the train K534/K535 to Yingtan departing at 19:04 and arrivinf at Yingtan at 01:00. Then you can transfer to the train to Huangshan: K162. It departs from Yingtan at 02:35 and takes about 6.5 h to Huangshan.
2. You can take train K135/K138 at Changsha departing at 18:56 and it arrives at Yingtan at 00:04. Then you can transfer to train K126 or K26 to Huangshan.
3, You can take K157 at Changsha, which departs at 14:30 and arrivea at Zhuzhou at 15:10. Then you can transfer to K156 departing at 18:01. It would take about 10 h.

By the way, you'd better buy the train ticket in advance. The following website may help you.
https://www.travelchinaguide.com/china-trains/