If you just learn to play, or just to exercise your rigorous thinking in mathematics, I suggest you find a book on advanced mathematics in liberal arts and do a little bit. After all, English is also a very good major. Learning well will be much better than math major, hehe.

If you are going to take the postgraduate entrance examination in economics or management, you have to study hard. You can watch the fifth edition of Tongji University (this is the designated textbook for postgraduate entrance examination) or spend less time on undergraduate courses. You can also study in advanced mathematics of economics. You can take classes in shifts, as long as you sit at the end and don't make trouble, the average teacher will allow it. It is still very impressive when English majors change to management or economic postgraduate entrance examination. After all, English is better. There are several management doctors around me who are transferred from English majors, but they can only study mathematics, otherwise it will be difficult to graduate, because economics and management are basically mathematics at the doctoral stage.

I hope the above answers can help you and we can communicate again.