Hello, i would like to know what is the last overnight train departing from Hangzhou to Guilin?

And what is the cost for a soft sleeper and what is the best way to purchase the ticket? Would I be able to purchase the ticket the same day or do i have to purchase in advance? I am aware this is a long trip but i want to explore at least one time an overnight long distance trains during my trip, however is it actually safe for tourist to travel in long distance trains? we are traveling as a couple.