You have to play online everyday to get the skull with the knife but K/D doesn't matter in zombies because that doesn't measure skill what so ever. If you wanna get better go play tranzit in custom with headshots only by yourself or Die Rise Headshots only, Welcome to zombies hard mode.
Your rank only moves up when you play live games. Not private matches or custom matches.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.