Howto stop over thinking?

I usually just research on google but maybe something more personal would be better. I'm 15 years old and I always overthink everything. I always try to think logically and reasonably or stress over things that I shouldn't be stressing over. How can I stop over thinking everything? Sometimes I feel like I'm an old person, but I wanna live and think like a teenager. So I can have more fun and relax.