Did you create the Desktop File?
Did you replace the generic "user-name" in the script with your actual username?
this file in this directory ~/.config/autostart
username changed sure
where this file should be ? in the .config/autostart or where ?
update I was working online and when I wanted to save some files and the window of saving opened the script stopped and the brightness of both monitors became 100% I needed to run the script manually same as I'm doing when I'm turning on my laptop
also I have this in the Startup Applications Prefrences
and still not working with the startup I'm running the script myself each time I turn on my laptop
That file can be saved in ~/.local/share/applications
I notice that the guide has an error where the content it has you copy and paste does not drop down a line for several entries. It should be:
[Desktop Entry]
Type=Application
Exec="/home/user-name/dimmer-startup.sh"
Hidden=false
NoDisplay=false X-GNOME-Autostart-enabled=true
Name=Dimmer Script
GenericName=Dimmer Script
Categories=Utility;
StartupNotify=false
Comment=Dimmer App to control screen brightness
The save dialog had this effect?
Would you be willing to burn a copy of Zorin OS 16.3 Lite on a bootable USB stick and boot into Try Zorin and test if you get this same effect?
I created file dimmer.desktop in this directory and I used this script
and still the scrip not running with the start up
I am at a loss at this point. Everything shows that it Should Work...
and now I got another problem that after suspend the brightness level reset to max
I searched and tried to fix and in the directory of /sys/class/backlight/ I have these 2 folders
in the asus-nb-wml folder the max_brightness 10
and it's all files read only so I can't change anything
same for brightness
but in the intel_backlight
brightness & max_brightness 5273
and also all of it read only
the problem still makes me mad and the more problem even after I run the script myself after startup when I open Discord it resets the brightness to maximum sometimes 
No one can blame. Nothing is more infuriating than that which should just work not working and trying fifty different suggestions only to have them all fail.
This is infuriating to me, too. I cannot fathom why it is that launching Discord would affect Screen Brightness Control.
If this was me, I would actually reinstall Zorin OS.
OMG 
reinstall for me it's a real problem according to my work and installing all my programs and accounts again but thanks in anyways
We may need to more closely examine what you have installed now, then.
How did you install Discord: What format was the package?
I recall that you added a repository and packages in previous attempts like sysvinit-backlight which is not applicable on your systemd system. Did you remove all of that packaging and any configuration files for it?
How I can check the packages ?
I downloaded discord from the official site and I used the .deb file
but actually it's sometimes happens with discord 1 time it happened when I tried to save a pic from brave browser
but it happened many times with discord that's why I thought it about discord
So, it may be near-coincidence? It happens when certain applications create enough graphical action on the screen?
most likely
Can you please remind which graphics you are using:
sudo lshw -C video
GeForce 740?
Which driver are you on?
probably the GeForce
What is the terminal output of
nvidia-smi
?
not found
which one I should install ? 
You may need to follow this post here:
...In regards to your graphics card drivers.