I am doing very bad in a lot of my classes. Besides making a schedule, are there any other good tips to suceed? (Please answer truthfully to me)

Do you do your homework just to get it done or do you actually do your homework to learn from it? If you can't teach others how to do the homework clearly then you don't know the subject well enough and should study it more. Homework is only there to help you learn, not punish you. Here in college, homework is only worth 5% of the grade, test makes up for 95% of my grade.

I recommend you write down the explanation to each of your homework problem and show all the steps and see if you can explain those steps.

Do you study ahead of time before quizzes and test? Don't study the day before, try studying 3 days before the test, or if you can, a week before the test. Your test determines the majority of your grade, so put alot of effort into studying for those.

Also, there's tons of online resource to learn from. and if your teacher have office hours, stay after to get some help on the subject.

Ask for help and ask for tutoring from your teacher.

parallel lines or skew lines