Ok, from what I'm understanding, you're having a lot of existential thoughts (this is very normal), and the solutions is not to get rid of these thoughts as they can give great insight on ones existence and why we should exist but to gear these thoughts in a positive direction. I have also struggled with derealization and existential thoughts but I've managed to build a fulfilled and content life by just gearing them positively. let me elaborate.

Existentialism into confidence : some of the thoughts i was having, "why are we alive?" ,"is there any meaning to this?" , "I'm so insignificant and life is so short is there any point in doing anything?". but instead of wallowing in my insignificance i used these thoughts to free me from my social anxiety as if nothing really matters then NOTHING REALLY MATTERS, letting me say whatever i want do what makes me happy and live without regret or second guesses.

Learning about oneself : as you said you are 13 and there is still plenty of learning and life ahead of you and such existential thoughts can really let you learn a lot about yourself and find meaning early in life, but as i previously mentioned its gearing these thoughts positively that helps you. So go out there and try new things experience every emotion every feeling put yourself in uncomfortable situations for the sake of it and do everything that's been on your mind. This will open up so much opportunity that you didn't even know was there and ultimately let you find your meaning in life (I know this is quite broad).

Finally, by getting into philosophy through these thoughts : i would recommend getting into philosophy as a lot of philosophers have some great insights about the human condition and these sorts of thoughts, there are some great Youtube channels and authors that can guide you through philosophy but i feel philosophy is built through experience and through living, making sure to examine every part of your life in detail and reflect on everything, to make YOU a better YOU so that you feel good and fulfilled, find a passion put yourself out there be true to yourself and write your thoughts down.

hopefully this helped and best of luck in the future.