taking a train in China

Hi, I'm Italian. I'm coming to China on vacation and planning to go by rail from Beijing to Pingyao and from Pingyao to Xian. I was about to buy the tickets, but to choose the most suitable timetable for us, I would like to understand how long in advance we have to arrive at the railway stations, in case there are security controls like in an airport, if there are indication in English inside the stations.

Thanks and best regards
Micol Metalli