I’ve uploaded everything on github here’s the link.
There is nothing wrong with your C++ code. I have zero experience with Visual Studio but seeing all those red minus symbols before each file except main.cpp makes me think that maybe they are not part of the project or are excluded in some way. When I look in the .vcxproj I only find main.cpp there.
So what I think is happening is that it only compiles main.cpp. This is consistent with the linker error messages that you got above. I.e. it doesn’t find the implementation of the constructor and other member functions of the Game class because Game.cpp is not being compiled (and linked).