How can I change the dark color of a vanilla “Gnome” Shell-Theme into the white(-ish) default “Gnome Classic” Shell-theme color?

How can I change the dark color of a default “Gnome” Session Shell-Theme into the light (white-ish) default “Gnome Classic” Shell-theme color?

It should be possible (at least, in my understanding) to do so without much effort, since I can already log in to a session (Gnome classic) that shows that theme version perfectly installed and working. Unluckily, I didn’t find anything that can explain how to do that online…

Here are my screenshots, in order to better understand what I mean:

MY VANILLA "GNOME SESSION" Shell Theme https://ibb.co/GkMC8y0

MY VANILLA "GNOME-CLASSIC SESSION" Shell Theme https://ibb.co/1fbC3t4

(the latter - long story short - is the theme I want to apply to my regular “Gnome” session)

I have “Gnome Tweaks” installed and “Shell Themes” extension activated (but the white theme simply won’t show anywhere for me to be able to select it)

mkdir -p $HOME/.themes/light/gnome-shell
cd $HOME/.themes/light/gnome-shell
cp /usr/share/gnome-shell/theme/gnome-classic.css ./gnome-shell.css

Open Tweaks and activate the “User themes” extension. Close Tweaks.
Then go to Tweaks -> Appearance -> Shell, change Default to Light.

Regards.

Thank you very much Antonsh. That worked perfectly!