Chocokyatto: Used the other downloader you guys have been suggesting. Got a checksum error after downloading for awhile. Is this the real life? I'm just gonna torrent the game at this point.
Strange. Okay. How about this.
Step 1. Download Free Download Manager.
http://www.freedownloadmanager.org/
Step 2. Install the program, then make sure you check the plugin which allows you to download from browsers using Free Download Manager
Step 3. Open Internet Explorer, should ask you to enable a plugin for Free Download Manager, allow it.
Step 4. Log into GOG, hover over ACCOUNT, then click LIBRARY, and click The Witcher 3, and click each download link to all the parts. Hopefully Free Download Manager will pick them up and download them with pause support and all. Be sure to accept Free Download Manager's offer or you're going to download using the basic downloader.
That's what I did with my Desura collection, and this should work well for you.