Nowadays, many companies have requirements for foreign languages when they are looking for jobs after graduating from college. I hope you'd better have level 6.
As we all know, China's mathematics level still lags behind that of foreign countries. If you want to learn more deeply, you must read the original English, which also requires English. If you want to further your studies, the importance of English is even more self-evident.
In a word, English is an important tool and means. If you master it well, you will have an advantage over others.