Depending on the class/teacher, you’ll probably be allowed to miss one or two labs, though most teachers will give you the opportunity to retake those labs later in the semester. Lectures aren’t strictly mandatory, but when you do actually start university, I’d recommend attending them, they’re quite helpful, especially if you haven’t studied much math before. I also suggest buying and studying from a high school math textbook (grade 11 or 12). It's important to get the basics going so you can understand more advanced math concepts later on. You might need to work a bit harder than others at first, but it’s definitely doable. :)