It's a basic human right that we, lucky Americans of all stripes have in writing; Freedom of religion and Freedom of speech. If I lose that case in court, every American loses that right too.
China is still atheistic communist to the core. The west tends to forget this at its peril.
Don’t go to church in a secret location the government does not know about and you will have no problem. The operative word is underground and the Chinese Government will never tolerate those kinds of meetings. Private assembly is illegal in China.