How to bring my marks up from beginning of semester : Grade 12?

I'm currently in second semester of grade 12, I have U English, U physics, and U data management. The first month has just ended and the second has started of the 5 months in each semester. i'm not doing too good in my cles for university standards, I have a 65 in English, and a 60 in data and around a 57 in physics. By the end of the semester I'm hoping for a 80 but mid 70's is still good. Does anyone have any advice on how to get my marks up and keep them up by midterm