Hi, please tell me how can I travel to H.K. and Macao during my 3 weeks stay in Guangzhou?

To Hong Kong, you can take high-speed train at South Railway Station, get off at Shenzhen North Railway Station. It just takes around half an hour on the way. Then take subway Longhua Line to Futian Port. After arriving, pass the custom and you will enter Hong Kong area.

Or you can take a train from East Railway Station to HK Hung Hom Station directly.

To Macau, take a train at South Railway Station, get off at Zhuhai Railway Station. The duration is about an hour. After arriving, walk to Gongbei Port and pass the custom to enter Macau.