First of all, there is no direct bus from Liuyang to Nanxian. You can take a bus to Changsha first, and pay attention to the west station. The departure time is also early. According to the bus schedule, there is no bus after 10, so you should leave early. In case you can't make it, you can go to Yiyang first, which will be a lot. Then it is also very convenient to go from Yiyang to Nanxian.

Then, I'm not sure when. It will take you about four hours. This is on the premise that you get on the bus smoothly.

Finally, Nanxian County is next to Dongting Lake. You can visit Dongting Lake, take a yacht (there used to be), or visit Huarong on the other side. Nanxian used to be a thatched street, and it was very lively when there was a ferry.

Finally, I hope you can catch the bus and have fun.