how far is it from Hongkong to Tianji, what do they require visa? get where what is the fastest means

The best way is to take flight from Hong Kong to Tianjin and it is about a 3 hours flight journey between them. You are not required visa to HK for 30 days, but you need to apply for a China visa to visit Tianjin in advance through Chinese embassy in Uganda according to your visit purpose, for example, visit China for tourism, then a tourist visa is required.