The bad news: bicycles in China break down. Often. We once had a new (cheap) bike which lost a pedal in the first two weeks we owned it.
The good news: there are skilled bicycle technicians on call at almost any streetcorner, and they work for cheap. A new brake cable is 3 kuai (45 US cents) installed, and patching an innertube is 2 kuai.
Here are two of five (!) bike repair shops within one large block of our house:
My usual repairman did not want his picture taken, but I think he’s a super guy: