Apple ID hacked

I received a message, a popup on my MacBook saying something along the lines of "your Apple ID is now being used for iMessage on conte's iPhone". I don't know a conte.

I was not asked if wanted to approve or decline this use on "conte's iPhone". When somebody from China wanted to access my Apple ID in the past, I was alerted by Apple and was able to decline. Not this time.

Anyhow, I immediately changed my password. But then a little bit later, I received an email from Apple saying: "Find My has been disabled on conta s iPhone".

What other steps should I take to protect myself from this conte person?

Thanks, Hans