Gas fees can be adjusted. There is a minimum charge for a transaction and users can opt to pay higher gas fees in order to speed up the transaction. Miners are likely to verify transactions sooner dependent on the fee offered for making the confirmation. This is why some transactions may take quite long to complete. This is often experienced when sending coins and waiting for what feels like forever before seeing the coins reach your wallet. The lower you offer to pay in gas, the longer you wait for verification and completion of a transaction.