What's the fastest way to get from Shenzhen North Railway station to Hong Kong, Causeway Bay?

You can take metro line 4 at the North Railway Station to Convention Center Station and transfer metro line 1 to Luohu Station, Exit A2. Then you may walk ahead to the port to go through the immigration procedures to Lo Wu Port in HK. Afterwards, you can take East Rail Line from Lo Wu Station to Kowloon Tong Station and transfer Kwun Tong Line to Mong Kok Station. You may continue to take Tusen Wan Line to Admiralty Station and transfer Island Line to Causeway Bay Station. The whole trip will take around 2 hours.