After WD40 lubricant and higher temperatures did not change anything I am convinced that somebody had messed around with the bike lock making it not opening anymore. I quickly decided to forcefully open the lock, but I did not have the tools. Unfortunately it is currently Chinese New Year holiday which means: All shops are closed. So also the nice hardware stores. But after 4 days without my nice bike I found a small hardware store that was already open. I never had been to this store. I walked in and asked if he could help open my bike lock. He first offered me a tiny saw. I told him I need some thing bigger. So he brought this huge bolt cutter (or massive pincer) and it went through the bike lock like a knife goes through warm butter. I was happy but also shocked. I hope my Kryptonite locks are more resistant.
I love Beijing for making these things so easy. I did not need to buy any tool, the hardware store let me use his tools. And the shop owner was really helpful trying to assist me – and that being free of charge. This attitude makes living in Beijing easy.