Left click+dragging cursor=some wierd glitch or something

Greetings guys! I have an extremely annoying problem. I use Windows 10 and whenever I play a game (as long as it's in fullscreen I suppose) and I press left click and drag the cursor to the bottom right (usually in shooters when I perform or at least I try to perform a sick flickshot) the taskbar appears and the cursor appears and for a second I can't control my camera view (in-game) and this had cost me a lot when playing anything. And when I don't have any apps opened and it's just my desktop and I do the same movement I can see a grey thing popping up from the bottom right (right there where's the peek to desktop button). Sorry if I didn't explain my issue properly. Thank you!
 
Yesterday I discovered that if I don't have any apps open (usually when I play I don't hide some of my apps) the problem is no longer but the bottom right side is still a sensible spot. I thank you for trying to help me and somehow you did! I wish you a good day/night!
 
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