How to save switching the screen mode

I made three checkboxes. Fullscreen, windowed fullscreen and windowed mode. If you enable one checkbox, the others are turned off. And everything works fine.

But. How I can save the mode settings to a configuration file? So that the next time you start game the mode settings are saved?

And further. When you exit fullscreen mode, the desktop resolution gets lost, how can this be fixed?

Thanks in advance for your help

Sorry my bad english

I am not sure of a clean way to do this but I personally just make my own settings save and make variables for like window mode as integer. then i do a load settings on init inside game instance then switch on that int for the 3 window types etc.

Thank. Made through an index. (with combo box) All three options work. But the settings are still not saved to the file.
(But I really wanted to make the option with three checkboxes)