Biscuit sets the Monero fee by itself from how busy the network is. The fee goes to the miner of the block; Biscuit takes nothing.
Turn on Settings › Transactions › Manual fee-tier selection and a choice appears on Send: Automatic, Low, Normal, High or Highest. A higher priority pays more to be included sooner when blocks are full. Most of the time, Automatic is right.
Subtract fee from outputs, on the same page, adds a Subtract fee from amount option on Send: the recipient gets the amount minus the fee, instead of you paying it on top.
A Monero block comes about every two minutes. A payment usually gets its first confirmation within a few minutes, and the coins received can be spent after 10 confirmations, about 20 minutes. Your change is locked the same way: see Balance.
Look it up on a block explorer: right-click it in History › View on block explorer.