Complete the game on any difficulty and just sit through the credits. The nazi zombie minigame will open automatically. Just play through it.
Even if you get munched on, after you die or finish it, the minigame will be unlocked. The game should give you a notification letting you know that it's unlocked. You can then get it from the mission select screen under Nacht der Untoten.
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.