- It's <Windows.h> and not "windows.h"
- You're using global variables - not only is this bad, but you actually have no excuse for using them like this since all your code is in your main function.
- All your code is in your main function (this will make it hard to refactor)
- You use the system command
But the number one problem is that you tried to make a game in the console. If you think you're ready to make a game, please don't make it in the console - it is actually a much more challenging task than simply learning to use a graphics library like SFML. I know you're comfortable with the console, but trust me - making games in the console is an incredibly difficult and frustrating thing to do and will not help you learn C++ better.