I sent $40 to some address and it's been 8+ hours and still no confirmation, so I don't know what to do. When I was about to send the payment, electrum's slider was on far left, meaning the smallest fees and "within 25 blocks", but seems like it takes forever instead. I saw
https://bitcoinfees.21.co/, but there isn't BTC/kB which is present in Electrum client, so I don't know how to calculate the optimal fee in order not to get stuck like now. From what I've seen on website, there is BTC per byte.