I can’t get to sleep easily because I can’t stop overthinking about bad things that have happened I don’t know what to do?

I'd suggest you try to do something active before you go to sleep. Not only will it release hormones that will contribute to your overall well-being but also make you tired physically and mentally, helping you fall asleep earlier without many thoughts. If that doesn't work, you can try sleeping with some white noise in the background. I find rain sounds particularly relaxing for this. I hope my advice was helpful. If you ever need to talk, feel free to message me! :)

I struggle with this often. I've found listening to guided sleep meditation (or something similar) really helps to keep my mind off of other things and focused on sleep.

-Try meditation. Trust me, if you meditate seriously, it can help sooo much with falling asleep ! -If it's a bad event that started with something you did (ex: you told your BFF's secret, and now the whole school knows and she's mad at you), I suggest you talk to the people involved and make the situation better. -If it's something that you haven't caused, I suggest that you open up to your closed ones about this problem, and the struggles you're going through. (of course, they have to be trustworthy). They will appreciate the fact that you opened up because it's a sign of trust, and you will feel much more relieved : a problem, when bottled up, only gets bigger and heavier over time.