My site have been hacked

Hello,
My website have been hacked, I first received an email from Google telling me that there is a “new owner” of my website with an email adress I don’t know
Then I can’t have access to my dashboard or anything wordpress related. And when I enter my website adress, the main page is on but when I try to click on any page on it I have this message
“Gone. ‘The requested resource is no longer available on this server and there is no forwarding address. Please remove all references to this resource.’”

Can you help me please?

The page I need help with: [log in to see the link]