Dealing with imposter syndrome is hard! What helped me was acknowledging that it is happening. Recognize that it's a common feeling, and even the most successful people feel it. David Bowie had it!
Share your doubts with friends or family or a school counselor. You don't have to go through this alone! Also try to be kind to yourself, you've made it to where you are by your own power, you're supposed to be there!
First of all, you should understand that the image that more experienced people create is just an image. Everyone has doubts and insecurities. Hiding them is a part of the experience. Second point: you are young, which means you have more time to learn and adapt to the constantly changing world. This is an advantage that more experienced people who have already gotten into the groove do not have.
I've always found that "imposter syndrome" is no different than being the "new kid in town". You're not somewhere wrong, you're not in over your skis, and you're not incapable of whatever challenge is ahead of you. You're simply new and learning. For me, that realization has helped to get rid of any lingering imposter syndrome. Remember the last time you felt like an "imposter" that wasn't this moment. That feeling likely disappeared as you got more comfortable with your new role and learned the skills that made you effective. That will happen again in any new role: all it takes is time, patience, and hard work!