Try the other one
I got it working but my game fucked up anyway. Thanks for the help.
Right click desktop, properties, settings and right click the other monitor and say set as default.
I tried but the option is greyed out, does this mean there is no way to do it at all?
You can't, that would require two computers. An external monitor doesn't qualify as another computer, and I don't think you can do two things at once. I don't think it's possible.
Yes, you can.