? I want to be an apprentice in a bakery. Xiamen, Beijing and Shenzhen, which city has the most developed baking industry, and which city can have more? ...

Well, as far as the three cities you mentioned are concerned, I personally think that the baking industry in Shenzhen is more developed because it is a rapidly developing coastal city after all. If you want to learn authentic baking techniques, you should go to Taiwan Province Province. It is understood that Chinese mainland's baking technology came from there. I am also engaged in this industry.