So basically there was no problem at first when I first installed manjaro it was running good and fastly. But yesterday when I downloaded a repo named (KWin Low Latency) and then uninstalled later on and now I’m not able to open System Settings its showing " System Settings failed to execute can’t load" something something like that. Then I tried to reboot the system and now I’m getting broken login page and I fix that somehow but when I entered to desktop it is black and blank and only cursor is visible
Can someone help me with this ? ^
Hello @RPS,
perhaps by uninstall the package you mentioned some dependent packages where removed too.
You can take look in the file ‘pacman.log’ which you can find here:
/var/log/pacman.log
You can also use this command to get a list which packages where removed (have a look at the date):
cat /var/log/pacman.log | grep removed
So you have a summary which packages you need to reinstall to make your system work again. 
Edit1:
The output lines should look like
[2022-01-02T16:51:25+0100] [ALPM] removed kvantum-qt5 (0.20.2-2)
… and tell the removed package (in this example) is called ‘kvantum-qt5’. Thats the exact package name. To install it again you can use this command:
pamac install packagename
Of course with the right package name! 
I short have take a look on the package you install/uninstall (KWin Low Latency).
In order to that it could be you unistalled a core package for KDE (kwin).
Plese try to reinstall this one first:
pamac install kwin