Where's MacOS 10.13 to download?

Delete any copies of "Install macOS High Sierra" from the Applications folder. Try while in Safe Mode.

How to use safe mode on your Mac - Apple Support

The item is available, open Safari and then click on the link provided by Dialabrain.

macOS full installers are only available through the App Store.

The page you showed earlier is from the Apple Support Downloads site. It only contains

updates to macOS's. These updates require you to be running a previous version of the OS

you are trying to update.

Moving from one OS to a newer OS is called an upgrade.

If when you get to the App Store and it says 'Open' then the App Store is noticing your mac has got a copy or partial copy of the Install macOS High Sierra.app in your Applications folder. Locate it move to your Trash, empty the Trash.

Make sure your mac is connected to your router via a cabled connection, Restart your mac, click on the link again,

the App Store should now say 'Get'.

Do not use the mac while it is downloading, do not use any other devices that share the same internet connection

while the mac is downloading.

Come on Helton, we know you can do this, your family and country are relying on you.

May the fourth be with you.

How to upgrade to macOS High Sierra - Apple Support

Helton Pereira Bastos wrote:

Thank you, but unfortunately it didn't work.

As stated, you need to be in Safari.

You're welcome.