However, I don't quite understand. Your grades are not very good. Why did you choose mathematics as your major? You should know that you should be interested in learning mathematics and at least have some perseverance. You haven't decided the direction yet. You should know more about various majors or occupations, find your own interests and choose related majors, so that you won't have any regrets in your later life!
If you want to be a teacher, I strongly recommend six normal universities directly under the Ministry of Education. Starting from the freshmen who entered the school in the autumn of 2007, six normal universities affiliated to Beijing Normal University, East China Normal University, Northeast Normal University, Central China Normal University, Shaanxi Normal University and Southwest University have implemented free education for normal students.
I wish you a brilliant life of your own!