Mouse cursor disappears when i open any game in fullscreen F11
Welcome to the Forum!
Do You use a third-party Cursor Theme or the default Adwaita one? And happens that, too when You use the maximize Window Button? And do the Game run over Steam or other such Stuff?
This is for your own benefit to prevent from unwanted clicks on the screen while playing any game. But if it not showing due to some technical glitch then update your mouse drivers or change your cursor settings.
Mouse driver in linux ? 
I fixed it in a few seconds, installed that extension 
and worked immediately 
.
Many users (specially new to Linux) had unexpected issues with Xorg and Wayland. Changing between them often solved many problems though. To see how it is, when you log in or resume from stand-by click the gear button in the bottom right corner and change it.