Take a look at whattomine and some of the information available and you will find the answers to your questions. Depends on the price of your electricity which you will need to look up to find out what you can estimate your profits to be.
Use mycryptobuddy, do NOT use cryptocompare. It's 100% misleading and will cause you to lose a bunch of money.
how can i know how much H/s RX560 or RX580 have?
electricity is about $0.14 per 1KWH
Depending on which card brand/memory, how they are configured and if the bios is modded you would get approx 10-14mh/s from an RX560 mining Eth and 26-30mh/s with an RX580.
Check which cards models are available to you and then search on here for that specific card to see the hashrate.