Time, once again, your best friend.
At home, manage your time efficiently and don’t simply do school work. You also have a life, friends and family. School goes second and I believe that if you use my advice, you will be able to have good grades. But don’t think you’ll have 100% at all times! Even if you’re organized, you must understand in order to succeed. The best tip to succeed is to NEVER get discouraged. (And don’t compare yourself to others)! Therefore, being organized makes the job easier and can help you succeed. I can’t help you understand your classes, but I can help you organize better for them!
Don’t forget one thing, more time you’ll invest in school to do homework and other things related to school, more free time you’ll have at home!