Is that correct now?

My monitor has 2x Hdmi and 1x vga. My PC also has VGA so I connect it to the monitor. I also connect my monitor to my Xbox one.

The question is: if I want to surf the Internet, I have to turn on the PC because Windows 10 is on it.

But if I just want to gamble, I just have to turn on the monitor, right?

And of course you also have to turn on the XBox. But do yourself a favor and also connect your PC via HDMI

If you don't want to use the PC, then of course you don't have to turn it on.

The screen registers that only your XBOX is connected, so it switches over to the XBOX.

You can use the buttons on the monitor (usually in the lower right corner) to select the source from where the image comes from or what should be output.

I can't quite follow your question, but logically you only have to turn on the components you need, so

you want to gamble on xbox needs monitor and xbox

want to use pc needs pc and monitor

You just have to turn on the device you want to use.

If you only need the PC → just switch on the PC.

If you only want to gamble on the XBOX → just switch on the XBOX.

The monitor too, of course.