can i reinstall sys-firewall and how
can i cheek my qubes os it works properly
need some videos to learn how use qubes os
from beginning to highest
sys-firewall is just a netvm - create a new qube, set its netvm to
sys-net, and set the "provides-network" property.
The default has memory 500, a green label, and is set to autostart.
I'm not sure how you would check Qubes works properly except by using
it. At a minimum you should be able to get online, open a browser and
open disposableVMs.
There is a guide at https://www.qubes-os.org/intro/ and there's a link
at the bottom of that page to "Video tours".
I'm told there is now a wide collection of videos on YouTube.