There are two shuttle bus lines to downtown, one is to Tianjin Railway Station and the other one is to Champagne Town on Nanjing Road. And there are five special bus lines from Tianjin Airport to downtown. It takes around 15 minutes from Tianjin Airport to downtown.

For the bullet train ticket, if you take the train at hot season like some holidays or festivals, you need to book that in advance, if in other time, you don't need to book since there are many trains a day. You can check for details of the train at China Train(https://www.travelchinaguide.com/china-trains/) .