Speak with your academic counselor after you’ve enrolled. There may be remedial classes or tutoring available. It depends on the school. If you want to go to Harvard, you’re in trouble, but a local school will probably cut you some slack. But be prepared to work hard. Also to be interested. Chemistry and biology are very relevant to everyday life.
Also, try the Schaum’s Outline series of study books. They present the material in a very understandable and business-like mannter, with lots of quizzes and self-tests, with the correct answers explained. If you’re really in the dark, try the “XXX for Dummies” or a similar series. Ask the librarian at your local library about what to get. And be sure your English reading and writing skills are adequate. College is reading, reading and more reading. And they’ll ask you to write a lot too, term papers and exams and what not.