Gas fees calculator | How gas fees are calculated?

I understand what gas fees are in theory but I wanted to clarify as I try to estimate what I'll be paying before doing a transaction.

Is the fee a one-time, not dependant on the amount of ETH transferred? OR is it calculated based on the amount of ETH transferred?

Hypothetically, if 5 ETH were transferred somewhere, is it the same gas price as it would be to transfer 1 ETH?

Are they based on the transfer or the amt being transferred?