So I just started this game and found out that there were cheat where you push C and type in Marvin. My problem is that when I push C nothing happens also I've binded C as parry; Don't know if that's the problem.

If I recall correctly, it's not the "C" button that's important, it's typing Marvin in the Character Sheet screen ("C" by default). Try opening the character sheet and typing Marvin there, no idea what button you've binded to that.

I binded that to B, thanks it worked.