How do I deal with bullies at school or confrontations in public/online?

Don't be as bad as them. If it's verbal or online abuse then don't respond and tell an adult as soon as possible. If it's physical, you absolutely must tell an adult straight away.

If you are severely bullied at school go to your teacher or another adult you trust and tell them your bad situation. Ask for help and support, it is not your guilt! Dont be shy to help for support. In the beginning you can try to seek support from your friends or peer group. You also can tell your parents, but its hard for them to intervene. Dont take the bulling behaviour personal. Most of the time bullies have problems with selfworth and emtion-regulation. In the long term they will get more problems in their life. But if the harassment dont stop, you must escalate this a step higher.