usually in offline installer you need to download the installer again if it has a higher number in the updates and a blue dot. Uninstall the game and install the new update. Except if it gets a small update then you can just apply the patch if available for your version of the game and add a new update withou the need of uninstalling. But not every game gets a small patch in the offline installers. Galaxy on the other hand you would need to connect your offline installer games in the main folder to connect to galaxy. You still need to have the games installed through offline installer and then just connect the folder to gog galaxy like C:\gog games and chhose check updates in galaxy and press update

so when it involves a patch, do I just install that patch into the original game folder? And how do I connect an offline folder with the "main folder"? I am not sure what you mean by main folder, if you could elaborate a bit, that would be helpful. And in turn, how do I connect it with GOG Galaxy? I really do apologize for all of these questions, I am not really knowledgeable with things like this, and I want to make sure I have a firm grasp on things while we text in this thread. So I am sorry for the multitude of questions that I am asking.

Check the picture updates, if you get a patch under like streets of rage 4 that i have the patch you only need to download it and install it from where you downloaded the patch. No need to put it in anywhere else if you already had a previous version installed and the patch simply updates the game to the newest version.
Or you could just get the offlne installers but all 3 parts have to be in the same folder where you downloaded, click it and install.

Now gog galaxy the gear icon has scan folders the gog main folder is where all your gog games are installed like mine are in C:\gog games and if you have any installed games with offline installer you can simply go under the tab installed games like parkitect here and choose update.

If you by any chance have a patch and dlcs like in parkitect you can patch the game but dlcs didn't get patches like that you need to uninstall only the dlcs and install them again with the new oflline installer.
Except if you use galaxy you just press the check upadtes and then an update button will appear if available and press that.

About what you asked you just need to download part 1 to 4 and press the installer and install the game. The patch files are only for like i have version 1.01 games and the update brings them to 1.02 without the need to download the whole offline installer so update will say patch 1.01 to version 1.02

Thanks so much for your help!! I really learned something today!! From what I am hearing (seeing), if a game has four parts - four files, I need to download them all, and then click on the first one, and my PC will then install all four files? And with patches/DLC, I treat them like regular game installation files, download them and put the game's folder as a destination? Do I have this right? I am not following what you said about uninstalling and reinstalling DLC.

Yes if it says part 1 to 4, you do that but remember that only the highest update number on the right are the new offline installers that are updated it either has a blue dot or a higher number then your previous version if you go the offline installer route.

The dlcs don't get extra patches sometimes i think so in the game folder parkitect i had to manually uninstall them and download the new offline installer for the dlcs and just install it.
Parkitect does have unins002 and unins001 exes to uninstall the dlcs and unins000 is the main game for parkitect uninstaller.
So reason for doing this in the offline installers is to get to the same version number
With galaxy it's a little easier to update, but that was how i was doing it before i had galaxy

Thanks so much for your help!!! I think we covered quite a bit in this thread!! I think I understand just about everything, still a bit iffy about installing DLCs, but if I have any more questions about them, I will put it in a new thread, so that if/when someone responds to it, people with the same question as me will be able to find it easily. Thanks again!!

I didn't bother to read all the other replies, and the first few did not mention the blue dot.

Many games at GOG get updates, with Galaxy automating how you get them, otherwise you need to manually retrieve them.

You can see which of your games have updates by visiting your online GOG library, where a blue dot will indicate a game with an update. So you need to browse to see all of them, but can reduce your list to just updated games with that option.

Be advised though, that viewing a game in your library clears the update indicator (blue dot), and from time to time all indicators get cleared by a GOG action. So it pays to check regularly, perhaps make a list ... or add a TAG to each game with an update, calling it something like - UPDATED.

It is also the case, that not every game that gets an update, shows an update indicator (blue dot), for whatever reason ... got forgotten or overlooked etc. The game The Long Dark is an example of that, which continued to get updates here after it left the GOG store.

Some games get patches as well as updates, so you don't always have to download a full update.