I’m not sure if I understood your issue correctly, but it seems that you’re in full screen mode, if that’s the case all you need to do is hit F to toggle between standard, full screen with menu and full screen.
If that’s not the case, then go to window and see if Application frame at the bottom is checked, if it is, uncheck it.
Regarding the masks, it really comes down to how you move the mouse/pen across the screen, maybe you are releasing the cursor too far from the image and you are getting an almost grey gradient which causes your image to fade evenly, try releasing the mouse before so you get a more contrasted gradient.
Hope this helps.