Dear Ms.alia,there a lot of restaurant serve halal food in GZ.Generally speaking,if the slogan in their Signboard includ words such as "清真"，“穆斯林”etc. will be ok.
Sorry to explain in such a confused way,but it's really hard to say. May be I can show you some pictures of usual Signboard.

i have eaten the malasian food befor .on it i saw the ward Halal.here in china also the same .when you see the resturant you can see this hahal.it maby halal and than you see if the workers looks like a muslim...........