First problem: after finishing all the downloads, and running the installer, it said part of it downloaded incorrectly. So i re-downloaded everything and ran the installer again, same problem. Decided to skip it instead of aborting the installer again.

Second problem: after installing the game and trying to run it I get this error message

Unable to load cooked 'globals\controls.csv'. Make sure resource was gathered and check log for details.

No idea what this means or how to solve this problem. Pretty bad experience for my first Gog purchase.

Any ideas on how I can fix this?

Are you using the GOG downloader? and downloading it you to program files?