Considering your present situation, it is a good choice to enter the graduate school of mathematics in Normal University, but according to your foundation, it seems that you need to make up the basic subjects of mathematics, such as line generation. We should also review elementary mathematics in order to take the initiative in our study. Students in this school can be math teachers. There is no problem teaching in Shanghai. Teaching in Shanghai requires some luck. Good middle schools in Shanghai are very popular, and doctors will compete, but if you have special skills, you might as well try.