How do I change the password for my Apple ID?

so my apple id is my gmail, but i think my icloud email got hacked. first, this morning, even tho i usually have like a million emails, i only had 2, and i didnt have any icloud emails. second, my dad got an email saying someone signed in to my account at midnight. third, while i was trying to figure everythin out, my content and privacy restrictions turned on. i know my screen time password so i just turned it off again. i changed my apple id password, but since my icloud email isnt my apple id, how do i change the password for that? and (i dont know anything about this stuff so….) how do i stop being hacked?? please respond soon!!

[Re-Titled by Moderator]