Any suggestion where to go while waiting for 8 hrs flight just close from HK airport?;)

You can go to the Disneyland.
Take the Airport Express and get off at Tsing Yi Station. Then transfer to Tung Chong Line and get off at Sunny Bay. Transfer to Disneyland Resort Line to the last stop. Afterwards, you can walk to the destination. If getting there by taxi directly, the cab fare is 100-110HKD!