First of all, I suggest you apply for part-time editing in some middle school math magazines. Now many magazines can review manuscripts online, so that you can give full play to your advantages without spending too much time. I studied mathematics in college and worked part-time in this field. )

Secondly, we can consider visiting several well-known mathematical forums in China.

People are often recruited to do some simple math problems, mainly to do basic work for some big math research projects or experiments, which is very suitable for undergraduates with good foundation. Not only can you earn a little money, but you can also exercise yourself. With the accumulation of experience, it is also good for future development.

Scientific research institutions that are too professional are not suitable for undergraduates to join the discussion. The key is that it is difficult to find money from them, hehe. It takes too much time and energy to open a shop online, not just to open a shop.