2. Do you need to compare if you don't learn well, or compare with now? Compared with the mathematics field at that time? Kangxi's mathematical level at that time was not middle and lower reaches.

Interest is just an introduction that can lead you into the door. Learning a thing well requires other factors, such as IQ, energy, information, resources and so on. As Emperor Kangxi, he had many things to do, and with the development stage of mathematics at that time, it was understandable that he could not learn well.