Is there a way to refresh the Display fusion,
because if I remove my second screen(I'm on a laptop) I first have to re open the icon in my task bar and press OK or Apply.

if you have DF pro there is an option to automatically fix your wallpaper which is what you are looking for. Its in settings.

No I don't
But I didn't understand the notification so I enabled that now and it'll do.

Anyway thanks for the help.