Monster Paradise - Chapter 3

I don’t understand anything at all.. First he started with a kitchen knife where tf did he get a gun from? Doesn’t say anything to the girl and she believes him somehow so i guess it’s a system weapon somehow? Then the rank system that seems total trash and 0 explanation. First you have Iron then it goes to gold according to the equipment explanation part.. Then you sometimes see bronze rank but i also saw black steel or something like that WTF IS THAT…. This is just a confusing mess.