So the question is : can we canceling the trasactions through decrease of fee(before get the blocks)? like do RBF with lowest sat/bytes ?
No, you won't be able to broadcast transaction with a lower fee. You can create a new transaction spending the same inputs and send them to your address with a higher fee than the original transaction. The latest version of Electrum allows you to do that automatically by right-click on transaction and selection "Cancel TX".