1) The fee of Ethereum is automatically calculated after setting the sending amount. The calculated fee is based on current average transaction fee on Ethereum blockchain network.
2) You can select the fee from "Slow," "Normal" or "Fast" or adjust it manually in the advanced fee settings.
If the fee is set too low, the transaction may not get confirmed in the blockchain network.
Advanced Fee Setting
The fee of ethereum is consist of "GAS fee" and "GAS Limit". You can manually set the GAS Limit and GAS fee on "Advanced" fee setting option.
The unit of GAS fee is "Gwei" which is one of ETH's sub unit.
1 ETH = 1,000,000,000 gwei
The real fee to be paid is calculated as “Used GAS amount” x “GAS fee” .
You can set the maximum amount of GAS as setting GAS Limit. Transaction can be confirmed faster if GAS fee is higher.