Hanoi-Nanning-Haikou

I would like to take the bus from Hanoi to NN. I believe it is the same station that arrives from Hanoi that I would depart from to go to Haikou. I am not sure what time the bus arrives in NN from Hanoi so can someone tell me the times of departure to Haikou and if it is the same bus station that will come from Hanoi please, thank you.