stuck screw

Hi guys Trying to remove a screw that the previous house owner put in but it won’t budge. Dry wall but it has been drilled into the brick/stone behind. I have tried an electric screwdriver/drill, pliers and it will not budge at all. Also used wd40 on it and still no joy, any ideas?

Ive got a philips head screw that is stuck and the head is a bit worn from trying to remove it. I need to remove it to replace a broken upvc window handle. Its hard to get much pressure behind as the window obvs wont lock shut. whats the easiest way to remove it, should I try a thread...