Hi, Mr. Shryansh. Beijing for 4 day: Tian'anmen Square the the Forbidden City; Great Wall; apart from these, you can arrange another two days to see hutongs and bar street in Shichahai area, famous old streets and shopping. 3 Days in SHanghai: Nanjing Road, the Bund, drinking and dining at Xitiandi, Lujiazui and take a cruise on the Huangpu River.
2days in Hong Kong and Macau is a bit shorter. One day in Hong Kong, you can go to Ocean Park, the Peak. You can find ferry to Macau late at night from HK-Macau Ferry Terminal. Macau is not big, you can visit the St. Paulo or the casinos.