I am newbe whose desktop is now bigger that the screen size, meaning I have to use my mouse or finger pad to reach all four edges. How to correct the screen size?
I am using a 15" ASUS laptop, with 1080X1920 native resolution. KDE Plasma 5.12.9, KDE Frameworks 5.44.0, Kernal 5.7.1 ,OS type 64 bit.
I don't know what changed, how to research it, or fix it. But it is a real nuisance that my desk top does not fit the screen. Thank you for help!

System Settings > Display & Monitor > Change your Resolution
Be careful here as if you pick one that is too small, you will not
be able to readjust later. Just go one step down and see if that
helps.

Thank you very much for helping me with this irritating problem!