HK to Hanoi (Vietnam) by train possible?

Hi :) I was wondering if the following journey will be possible without Visa: starting with the train at the new Kowloon West Trainstation in HK (suposed to open the next days...around 23rd September 2018), then two stops and change of trains in Guangzhou South and Nanning. The whole journey from HK to Hanoi will take less than 24 h. (German passport holder). Thank you very much for your Support :)