Hi, kind of a newbie here.
I have been using Linux since one year ago and KDE only since a few months ago. This is the first time I find major issues. As usual, I have been doing some research online but this time I could not find a solution that works. I was hoping that somebody here could help me to debug and solve some problems that just appeared after the last update of my KDE Neon. The issues I have:
-The computer does not reboot or shut down. It gets stuck in the logoff screen with the gear icon turning endlessly. I always have to restart or switch off manually with the button on the PC. This is reproducible when shutting down from terminal too.
-After booting, I see a blank screen for about a minute. Then the login screen shows up but the whole system is way slower than before. It takes about two minutes to show the desktop, the toolbar and the two plasma widgets. Opening any app like Dolphin or Discover is painfully, usually showing just the frame of the app window with just the desktop background frozen inside for some time until the app finally loads.
-When using two monitors, I can't change their position in the settings anymore. The icon changes to "drag-and-drop" shape, but it moves the whole settings window instead of the monitor position.

It looks like one of the problems is related to the graphics rendering somehow, but I do not know if is linked to the shut down problem too.

What I have tried so far:
-Disconnecting one of the monitors: made no difference on the system speed or the booting up problem.
-Deleting the ./local/share/screen folder content in order to reset the monitor settings: no effect.
-Searching and installing the latest Nvidia drivers from Ubuntu using the terminal: did not solve anything either.

My hardware and system info:

KDE neon 5.24
Kernel 5.13.0-27
CPU: Intel i7-6700K
GPU: Nvidia GeForce GTX1070

Any hints on how these issues could be solved? I made a backup copy of my home folder and the rest of the system a couple of weeks ago using KBackup. Could I just try restoring some files and folders from there to solve the problems? In case yes, which ones?

Any help will be very much appreciated.