When to read ang in Japanese and when to read n? For example, how do you pronounce ぇんぴつ, こぅぇん, マンション? Why do you study?

If Japanese does not distinguish between these two sounds, it can be pronounced correctly. It's just that you are from China, and you are used to listening to sounds. If you listen to them more, you will know that the Japanese pronounce these two sounds casually. I used to have a Japanese friend who used to joke about it. He told me that I went to heaven to play yesterday. Actually, it's about Tiantan Park. People in Shanghai and Guangdong cannot tell the difference between these two sounds.