The G613 wireless mechanical gaming keyboard has a switch that lets you turn Game Mode on and off. In Game Mode, the Windows, Menu, and FN keys are disabled to prevent unwanted interruptions. To enable Game Mode, push the Game Mode switch to the right, as shown: 

In addition to the Windows, Menu, and FN keys, you can disable other keys in Game Mode using Logitech Gaming Software (LGS) 8.96 and later. If you don’t have LGS, you can get the latest version from the Logitech Gaming Software download page. 
NOTE: LGS does not detect the G613 gaming keyboard while connected to a computer in Bluetooth mode.

Launch LGS, select your G613 gaming keyboard and click the Game Mode Settings icon.

The Game Mode Settings window appears:

Enabled keys are shown in blue, and disabled keys are gray. To re-enable a disabled key, click on the key again. You can disable keys in Game Mode for any individual profile.

NOTE: The Windows, Menu, and G-keys cannot be enabled in Game Mode.