The key to understanding what you have read is to keep on reading, every single day. Attempt to take notes as much as possible after each page. You may even ask yourself questions at the end of each chapter to "refresh" your mind. Try not to be discouraged if you do not understand a passage the first time; try breaking down each passage as you go along. You may need a tutor that can teach you reading comprehension, if you are struggling a lot. Although your comprehension capacity may be below average, DO NOT give up. You can use resources such as "cliff notes" to help you summarize different passages. Do not hesitate to reach out to a tutor (like me) for extra help.
Good luck,
Mia A.