And voila, that did the trick.

dont all linux users change their distro once a year?:O
I thought that is mandatory

Some people just want things to work, no matter what engine is running under the hood.
I can understand OP confusion, as someone who tried Linux "BeCaUsE iTs FaStEr AnD sO mUcH bEtTeR" and knows little about computers, I had a really hard time even make it to boot, let alone understand how to change the kernel to the only version wich supported the graphics accelerator on the dreaded netbook.
SPOILERS: it was actually much faster than with Windows, even without GPU acceleration youtube could play a resolution or two higher.

Yes, but only until discover of Arch.

Why is EVERY thread about Linux ALWAYS derailing into distro-war? xD
And people wonder why Linux community is off-puting to many.

- I have this simple problem with distro X
- Oh no, how dare you use distro X?! You should change to Y at once.
- Distro Z is much better though.
- I use arch btw.

Very astute observation.

Welcome to Linux and Ubuntu is the best choice.

Installing programs on Ubuntu is extremely simple. But there's one main difference of Linux with Windows.
--------
On MS Windows, file extensions determine the file type. *.exe is an executable, *.txt is a text file.

On Linux, the file type is determined "inside the" file and can be altered. This ensures maximum security and is one of the main reasons why Linux is far more secure than Windows.

So on Linux, you can create a file, and name it my_file.txt. Open it with a text editor, write some code, then make that file an executable and run it.
--------

Now back to your situation. The files you downloaded are not automatically executable. If you trust the source, the easiest way to make it executable is:

"right click the file >> properties >> Permissions >> Check "Allow executing file as program"

That's it. Now you can double-click it and it will run as intended.

---- EXTRA ----

Linux thrives on "packages", a group of shared codes that makes the systems run. And as systems improve, some packages are "dropped" in favor of others. And since most GOG installers assume (or expect) some packages to be available by the system, some old wraps may not always work.

In order to see what the problem is, the best way is to run the package in the terminal, so you can see what you are missing. Let's say that your game installer is called Game.deb (It can also be game.ls. The procedure is the same)

1. Go to the folder Game.deb is in. Do this the "windows" way, normally, without the terminal.
2. Now right-click anywhere inside that folder and select "Open in Terminal". The terminal will open in that folder
3. type
ls
This will list the files and folders inside where you are. Make sure that Game.deb is one of them.
4. type
./Game.deb

Note that if you just type ./G and then press TAB to autofill. Press enter.

TRAP!! Linux is case sensitive. So if the file is Game.deb, and you type ./g and press TAB, it won't auto fill. Also, it won't run if you type ./game.deb or ./GAME.DEB .

I love trolling my windows user friends by sending them 5 different files named like (game, Game, gAme, GAME etc), and then they can see all 5 files but can't open them unless they can solve the puzzle. A fun mental exercise.

5. This will try to run the file and output any errors with missing dependencies along the way.

ENJOY!

Because the Linux community is toxic. And you might be surprised that this is now actually a documented fact. Most toxic Linux users take Linus (creator of Linux OS) as their role model. Linus was banned from the Ubuntu community. He had to take psychological treatment and had to publicly apologize for his unacceptable behavior to be accepted back. He now behaves rationally but unfortunately, the rest of his followers failed to exercise his redemption.

Now whenever I recommend someone Linux, my biggest warning is to stay away from those people. You'll ask a question and they will throw all their knowledge, except the actual question you initially asked.

Why would i do that? I get a working state and i keep it. Occasionally i'll update a library or app if it seems necessary, like if i want a new kernel feature.

Also to note, Richard Stallman disliked Ubuntu over privacy concerns of how it was made to preemptively act and end up giving out data on you.

Oh? Not that I'm surprised, just wondering how/where this is documented.

Search for "Linus Torvalds's apology" and you'll eventually find his psychological mental reports. From the scientific perspective, "documented evidence" means proof of something filed by an expert, in this case, a doctor.

Since Linus himself described his medical analysis as "toxic" over the last 3 decades, it is logical to categorize everyone who follows the same path, practicing the same behavior in the same regard. That was the basis of my verdict.

I found a few links, but I don't think it is fair to post them here, as they were too in-depth. Linus is actually someone I really admire as a creator and his usually selfless behavior. I just don't appreciate his -now thankfully in the old times - God-complex, where he tried to control everyone and everything and felt the right to dictate what every Linux user should use.

He disliked tons of other things as well but I guess you don't care about those or you wouldn't use website utilising proprietary javascript. Or maybe you browse GOG forums via wget fetching to e-mail?
Of course Stallman is always right, unless he isn't but then we don't talk about it.

cause yutubers will say you what is the newest hype distro and you should install it already

This worked for me, on ubuntu 20.04.

Here are gog installation instructions:
https://support.gog.com/hc/en-us/articles/212454349-I-cannot-run-the-sh-installer-or-start-sh-file-help-?product=gog

I use Mint instead of Ubuntu because Mint doesn't try to push me to use snaps etc. like Ubuntu does. Mint is like the cleaned and sanitized version of Ubuntu.

Ubuntu has been adopting all the wrong ideas from Windows, and Canonical apparently thinks it is the Microsoft of Linux. At some point Canonical suggested Ubuntu shouldn't be called "Linux" but that it is an OS of its own.