What kind of classes are you in? Some colleges have “weed out” classes in things like intro chem. In STEM classes, you will often find students in intro classes who’ve had the course material already in some other setting, so you might not be starting from the same spot.
Is there free tutoring available from the department in classes you are struggling in? If so, take advantage of it. If not, consider paying a tutor.
If you do poorly on an exam next semester, take the time to go over the questions on the exam. You may be able to anticipate where the prof is taking the material from next time around and what kinds of questions they ask to help prep for the next exam.