I have already downloaded a Witcher from GOG. On the official page I found a two patches: http://www.pl.thewitcher.com/the-witcher/1/
Do I need to install them or there are already added to the gog version and installed with the game together?

The game comes fully patched

And yet when I run the game that I downloaded last night it says it's version 1.4.5.1304 ..... not 1.5.

I downloaded the 1.5 patch and it said it couldn't determine the version I had on my PC.

I'm confused. Could we get an official answer on this?

That happened to me too, with my disc version of the game. The menu bar is unreliable. Instead, find witcher.exe in your game directory, right-click it, go to properties, and look for the version there. It should be 1.5 (this has been verified by several people running the GOG version).

Another way to check is by seeing how many extra adventures are included with the game, as several of these were added with the v1.5 patch. Launch the game, choose new game, then choose "new adventures". There should be six or seven adventures in there. Most of those were added with v1.5.

In short: The GOG version is indeed v1.5, even though the game window claims to only be v1.4.5. I think that v1.4.5 is the LAUNCHER version, rather than the game version.

Yes, it says that in the taskbar for the game if you Alt+Tab.

However, if you check via Game Explorer and also "witcher.exe" (right-click, Properties then Details tab), you will see it's actually v1.5.0.1304.

Cool! Thanks for that. I was a little worried.

AFAIK EAX only works with certain creative cards .