can i get a train or a bus from hong kong airport to guiyang city

Neither the train nor bus exist between HKIA and GY.
You need to enter Shenzhen and fly to GY or head for Guangzhou and take a train for GY.

Hi how many hours will it take to travel from hk to shenzen to catch a train in going to guiyang thanks

Well, you can take East Rail Line to get to Lo Wu Station first. Starting from Hung Hom, it takes about 45 minutes.
Then pass the custom and walk to Shenzhen Railway Station. After that, you can find the train to the destination. The train ride takes about 22.5 hours.