I would like to know how you can prevent people stealing stuff out from you and how to make bullies stop?

I've had that kind of stealing happen to me before too and it infuriates me still, and that was six or seven years ago when I was in junior high. I'm not sure I can specify which is better to do when, but sometimes it's best just to ignore the person (or more specifically what the person is doing or saying) and sometimes it's really effective to kill them with kindness. And I don't mean fake kindness, I mean real, sincere kindness. Be kind to them, truly, it will drive them crazy. However this does only work with certain situations - I would lean more toward name calling situations and the like, not the stealing and such. Other than that, I do not know. Best of luck.