PLEASE TRY TO DOWNLOAD THE GAME USING GALAXY
In case if your setup files were corrupted during downloading via browser, then please try to download this game using GOG Galaxy. Firstly download and install latest version of Galaxy from here:
After installation run Galaxy and sign in with your GOG account.
Go to Library, select your game and click Install. Follow onscreen instructions. Game will be added to sidebar on the left. Click on it and when installation will finish and press Play button.