Problem with Eurotruck Simulator (ETS 2)?

I currently enjoy playing ETS 2 and have 2 monitors, I play on the first and watch streams on Twitch on the second. When I'm on the menu with ETS 2, the mouse does not bring me to the second screen. Is there a key code or something?

Are you in full screen or not? Try Alt + Tab

You can press the Windows key or tabby when you are in the Steam menu (Shift + Tab). And then there's the possibility of @ChiefyyFan.