Can Huadu District go to Conghua District to get the certificate?

No.

Huadu District and Conghua District are two different administrative districts in Guangzhou City, with their own civil affairs departments and certificate collection procedures. Marriage certificates need to be obtained at the civil affairs department where one of the men and women has their household registration, and cannot be obtained across districts. Residents of Huadu District cannot go to Conghua District to obtain the certificate. If you want to obtain a marriage certificate, you need to go to the civil affairs department in Huadu District to apply for it.