Dual Screen functionality

I have dual screen, and I am playing World of Warcraft on the first screen and I'd like to do other things on the second screen.
But, WoW's fullscreen won't let me go to the other screen, even when I try to use "Windowed Mode" the screen turns black (cmonBruh)
and the screen freezes.

Does anybody know how I can comfortably play WoW, as in: "Play WoW on one screen and fucntionally use the other screen also, so the mouse leaves the fullscreen game and can be used on the second screen, which u can still see the fullscreened game".

Anybody help??????

Greets, yours truly
PaprikaBoi