You would probably receive more help if you could be more specific as to what it is exactly you are trying to do. Yes, I know you want to "decrypt game.exe" but what do you mean by that? There are tools out there for various tasks such as what you mentioned but with the proper education behind you, you won't know what you are doing. These are not simply programs that you just click "Run" and it does everything you want for you.
One method used to view an executable is using a debugging tool that shows the assembler of the file. This is a viable solution but if you don't know anything assembly language, then it won't help you. One such tool that is used around here is called OllyDbg which can be found at https://www.ollydbg.de/