I just failed my midterm...?

One failed exam doesn't mean the end of your beautiful GPA. Like you said, you're good at ignments and presentations. Use that to your advantage. Strive for good marks on all your ignments and go above and beyond the requirements for your presentation. If you get an A++ on your presentation and really impress the teacher, he or she may feel bad about giving you a low grade overall due to one stupid little exam and may bring up your grade a bit. Also, talking to professors in office hours (or if you're in high school, talking to them after school) tends to bring your grade up slightly.