Actively defending against what I think is a ransomware attack

Hey, Guys!

I am actively being attacked by what I assume is a ransomware peddling slime ball. We are a small business, and my boss’ 365 account want compromised yesterday. I use my private gaming PC for working as well - with a local account that I use when not working. Anyways what I think has happened is that the scumbag got into my local account via the compromised 365 Admin account, and then reached my local account from there. All of our info is probably locked up by now (as soon as my Ethernet transfer activity surged, I unplugged my desktop. Could really use some help here, I have been up all night trying to counter whatever malware he was using. Cannot believe there is not a crisis number for paying businesses and customers.