Good day! Ms. Thanh,
Well, there are two trains from Shenzhen to Beijing. One is K106 departing at 11:06 a.m. and arriving at 04:08 p.m. the next day. Another one is T108 departing at 02:29 p.m. and arriving at 02:13 p.m. the next day. What else do you want to know? Actually you can search on this page https://www.travelchinaguide.com/china-trains/
you can find some basic information concerning these two trains.