You're young, recently bought Bitcoin, and can't remember how? How is this possible? It doesn't make sense.
Next, you'll say you don't know how you stored your backup seed.

There's a few more things to consider buying Bitcoin. You should probably study and cnosider it before proceeding.
Start with transaction fees: withdrawing a small amount from an exchange means you pay a large percentage in withdrawal fees. Collecting small amounts in your own wallet means you'll pay more on transactions fees when sending it later on. Keeping it on an exchange has risks, keeping it in a hot wallet also has risks.
It's probably best to discuss with your parents on how to create an account. If your under age, maybe they're willing to help you out.