What express should I send the documents to the patent office?

Just send it by registered mail through the post office It doesn't make much sense to use EMS if you are in a hurry. It is recommended not to use other non-post office express delivery.

According to the Patent Examination Guide, the application date of the application materials sent by post office shall be counted from the postmark date.

If it is delivered by other express delivery methods, the application date shall be calculated based on the date actually received in China National Intellectual Property Administration.