What is the default Session Manager and Font Manager in ZorinOS 16 lite?

Is Lightgm the default session manager?

There is a fonts program in the menu, but it doesn't respond and freezes the system. The task manager is showing it as gnome-font-viewer. Can it be repaired or i need to uninstall it and need a new manager?

LightDM is the default Display Manager on Zorin OS Lite.

See if

sudo apt install --reinstall gnome-font-viewer

works for you.

But there wasn't any lightdm settings menu until i have installed it and slick greeter myself.

True...
I always install first thing:

sudo apt install lightdm-gtk-greeter-settings

The Power of Settings