sting40000: it told me the first file is damaged what do i do
Re-download it manually in browser from the game page on GOG site. There are 7 parts, choose the broken one.
mageakos: if i restart next time will it continue or do i have to leave pc on to download all of it?
I really doubt Galaxy will resume download, though I've never checked it, managed to download whole game in one attempt. In any case I'd recommend to download the installer using GOG Downloader and then install the game. Galaxy will automatically detect it and add to the side panel ready to play on 19th (just checked it).