So I went through the payment process with bitpay (Bitcoin amount is around 1.8 mBTC), disabled in Electrum as they had suggested Replace-By=Fee and then pasted bitpay's payment url (
bitcoin:?r=https://bitpay.com/i/....) into Electrum.
I got to the send screen. But here I received the following warning: "The fee for this transaction seems unusually high. (20%)" as shown in this screenshot:
Why is the fee so high and how can I reduce it to an "normal level" like with credit cards (say 0.5-5%)?