If the account is in your name you're responsible for payment. But you can probably sue your manager for doing that. I don't see Hetzner's fault, they'll have to assume that you opened the account if it's in your name and was likely used by you.
But that's for you to pursue (to sue the fraudster would be a first step). Without a court decision, the counterparty has no reason to go after another person than the one on the contract.
