today i tried to withdraw and i got a message saying that the action could´t be completed because the "hot wallet was empty".... what does it means?

that the site does´t have the liquidity to pay the earnings???
It means what it says. Hot wallet is empty. Admin needs to transfer funds from the cold wallet to hot wallet.
Nothing to panic about. It's a standard practice to keep most of the funds in more secure cold wallet, meaning the hot wallet (which supports deposits/withdrawals) will sometimes run out empty.