Hi Lila, the train from Guangzhou to Nanning takes about 13 hours, and the last one leaves at 21:06 everyday. On the other hand, the last flight from Guangzhou to Nanning also leaves at 20:20 on Dec 2. So, you should stay one night in Guangzhou, or change another flight to arrive at Guangzhou earlier.

Actually, it is suggested that you fly to Guangzhou firstly and then go to Nanning by flight as well, vice versa. I don't think you could purchase the train ticket to Nanning on the spot.

Here is the flight and train search tool: https://www.travelchinaguide.com/china-flights/
https://www.travelchinaguide.com/china-trains/

Thank you so much, Mr. Shan. ^^