I do not understand why we have to pay for 4 cent per transaction tough, isn't that too much? Who decides the 0.0001 should be the optimal miners fee? How come I get lighting fast transaction if I pay 0.01 and I wait 2 days if I don't pay any?
The miner decides if your transaction will be included in their block. One of the factors in their decision is how much you are paying them. There is a (very small) cost to including a transaction and there is a limit to how many transactions that can fit is a block, so the miner is going to choose transactions with higher fees first.