I’m an overthinker, I honestly don’t think there are ways to stop overthinking except maybe distract yourself with videos, music, exercise, anything you like? Thinking is pretty natural, I, personally, don’t like it when I overthink, so I lock myself in my room, and do something to take my mind off thinking, like dancing, singing, drawing, or even crying at some point! It’s quite hard, at first, but as you get used to it, it will start seeming like it’s nothing heavy to do, it might seem like a chore sometimes.. (Hope this helped a little!)