I need a help y'all! I'm a beginner, I have RTX 4090 so I have no idea how to activate it or If I already did.
In "About" the graphics say: NV192 not RTX 4090 so I don't know if I did it correctly but it work fine and my Windowing System is X11.
I'm using "Using X.Org X server" at the additional drivers.
Hey there! That's definitely something I can help with: with or without SecureBoot enabled.
Based on your About page, you are using the Nouveau display driver right now, which isn't really great for gaming, but it is open source.
Nvidia drivers don't immediately come with the Linux kernel like AMD drivers do, so you'll just need to intentionally download them if you want them. You can do this through the Software Updater (most of the time).
Other times, you end up needing the Terminal (if the Software Updater fails to get them).
If you go to the Software Updater (it has a little orange circle with cyclic arrows), you can go to the "Settings" menu after it checks for what updates are available.
From there, you can go to additional drivers and give it a second to load the list of drivers.
For the most recent games, like Monster Hunter Wilds, I hear you need the newest 570 or 575 drivers to get a good experience, but I'm sticking with 550 because 570 wasn't great at switching between Desktops while not crashing the games I play (Tabletop Simulator). Monster Hunter: Rise still works perfectly on 550.
Select the one you want, depending on your needs.
If it finishes successfully, reboot.
The About page should reflect your Nvidia card, if it doesn't, that probably means that either SecureBoot is on or you are still using Wayland, which all 4 Nvidia cards I've tried hate consistently.
To disable Wayland (including on the Login Screen--I highly recommend doing this to prevent flickering nonsense):
sudo nano /etc/gdm3/custom.conf
Uncomment [remove # from] the line containing:
WaylandEnable=false
If SecureBoot is enabled, you can either:
If you have SecureBoot enabled and want it to stay enabled, I'll elaborate more on how to enroll the key, but it would involve a command like this:
sudo mokutil --import /var/lib/shim-signed/mok/MOK.der
Rebooting and enrolling the key. During the install of Zorin, when I told it to use a modern graphics card drivers and third party proprietary drivers, it tended to sign it, but not enroll it for some reason, and that would be the verbatim command you need.
When you reboot, you'll have to finish enrolling the Key in the weird blue BIOS menu that will show up.
If Software Updater doesn't install it successfully, then you'll have to install it through Terminal manually instead, which multiple people here (including me) could help you with if the Software Updater fails to do it, depending on which version you want.
In my experience, the Software Updater usually only has problems switching from one Nvidia driver to another (not going from Nouveau to Nvidia).
Let us know how it goes.
I agree with @chronosJ
(1) Disable Secure Boot in the BIOS
(2) At login screen, click name, click 
click Zorin On Xorg
(3) Use an Nvidia Proprietary driver.
What driver is shown in use when you go to "Additional drivers"?
Welcome to the Forum!
First, I would suggest to switch to Xorg like @StarTreker already described. Xorg is on Zorin 17 the better choice for using Nvidia Cards.
Then You should install a proprietary Driver for Nvidia. There are the default Nouveau Drivers but they are not so well. You can do that in the ''Additional Dirvers'' Tab like @StarTreker has shown on the Picture.
If You should already have done that or You installed zorin with Nvidia Drivers, we will make it now a bit different with the Terminal. First type:
sudo apt purge nvidia*
That will remove eventually installed Nvidia Drivers. Then type:
sudo apt autoremove
to remove Rests of Files. BUT: Look at the List of the to removing Files first before Your delete them!
Then, to install the Nvidia Driver:
sudo apt install nvidia-driver-[Version-Number] nvidia-dkms-[Version-Number]
Replace [Version-Number] with the Driver Version Number that you want use. Here an Example for the 570 Driver:
sudo apt install nvidia-driver-570 nvidia-dkms-570
No Thanks. I'd rather keep it as Xorg but thanks though.
Why would I need to replace the driver?
I'm NOT gonna to use Nvidia Proprietary driver since it messed up my display.
Also I do not see a gear icon at login screen.
Because a different Driver (Version) could work better with Your Graphics Card.
That is up to You. But it should work better together. In more modern Desktop Version Nvidia and Wayland can work relatively good together, too but because of the older Version that Zorin uses, it misses the Implementations for that.
When You go to Settings>About do You see there Wayland or X11?
Xorg is the same as X11. You are already on Xorg.