Help! I’ve been hacked!

Hi, so someone (somehow) hacked into my Instagram account and now have my Spotify account, I’m afraid this means they have more access to my personal information than I would’ve thought. So far, they haven’t done anything I’m aware of, but I keep getting emails informing me about suspicious activity on the accounts. If they’ve breached two accounts with different passwords—who knows what else they’ll be able to access! I know the obvious option here is to delete my Apple ID and make a new one, but I want to avoid losing my Mail data and other data I can’t transfer to a hard drive and whatnot. So, my question is, how can I block this hacker, create a new email, and keep all of my data? If it’s not possible, I guess I’ll have to just lose my data in order to protect my personal information, but if it is possible I’d really appreciate the help! Thank you in advance!