Dean478: 1. Using Firefox. I couldn't find them listed in Galaxy 2.0 and I don't have 1.0 anymore since 2.0 is installed.
2. I tried both Windows Explorer/Zip and 7zip but had the same outcome.
Then I presume something went wrong during the download, or GOG had corrupted versions available when you downloaded them, and fixed them before I downloaded them.
Below are the SHA-256 checksums for my working files. If you get some other checksums, I presume you need to re-download those files. I've listed the checksums also for the .mp4 video files but of course I can't know for sure if they are 100% ok for me (no way to verify data integrity for .mp4 video files, I presume). But since my .zip files downloaded ok on the first try, I presume the video files are ok too.
Since you have 7-zip installed, you can generate the SHA-256 checksums by right-clicking on a file and selecting CRC SHA => SHA-256.
Name: bonus_pack_french_.zip
Size: 1331544219 bytes (1269 MiB)
SHA256: F48FC700A76B1D80D40354D052123D4220C3557180F61D568E80B40CF4E0764E
Name: bonus_pack_german_.zip
Size: 1340260846 bytes (1278 MiB)
SHA256: 7125F3336C56A59950EE4A63731D9B36A89C97EB21734374976324ECDC48DB84
Name: bonus_pack_italian_.zip
Size: 565791001 bytes (539 MiB)
SHA256: 3B58F614CDF5FB24F909516D01F6C5E62DFB9D13BF61041683BE8E0C5B26B93C
Name: bonus_pack_polish_.zip
Size: 1343743862 bytes (1281 MiB)
SHA256: 62C257BA60D757054CC15CE65EA1001012206B69F9DE6916FADAE9F3158FD6C6
Name: bonus_pack_russian_.zip
Size: 807630330 bytes (770 MiB)
SHA256: FAE83E72F70A99B78623311C564E34D25A4A140305F6C80C6180A5BE4BBFA768
Name: bonus_pack_spanish_.zip
Size: 568974743 bytes (542 MiB)
SHA256: F1E1DDFC8F95C00053570C3053DECF66C8041A8C154928D7197C392FCAE703F2
Name: the_witcher_2_goodie_pack_part_1.zip
Size: 2511919950 bytes (2395 MiB)
SHA256: F3D6465221902B8BC55666B6626BA591BB1B988EBD504358472EFAF3D968C7EF
Name: the_witcher_2_goodie_pack_part_2.zip
Size: 2337086476 bytes (2228 MiB)
SHA256: FA1985DC3DC1C1096FAEC0088CB7E4D1F7F60A65A8A7CD70E05CA8980269A6E7
Name: the_witcher_3_goodie_pack.zip
Size: 4570219863 bytes (4358 MiB)
SHA256: 46AA4058B39DA57CF7539D731A6B4C89C5A531E24A49A3EB889A8ED8189C7653
Name: the_witcher_goodie_pack_part_1.zip
Size: 3423131034 bytes (3264 MiB)
SHA256: 34574D4C9F5E84873878DA00FA3782335E689CB14D0E50B7676CC7E0F865EB52
Name: the_witcher_goodie_pack_part_2.zip
Size: 1429316502 bytes (1363 MiB)
SHA256: F9633165DC6B9AC4F10F4532EFDF1E08279F8CEC00C0BFE7B4FCBB4C7BD7266B
Name: thronebreaker_goodie_pack.zip
Size: 2788707333 bytes (2659 MiB)
SHA256: 00E921361BF0596D95C3614AEDCF6D5F674618BA134998408E73BDA09D302A35
Name: 4K.mp4
Size: 21132529952 bytes (0 KiB)
SHA256: 0A419E7CF971279602EF1562B84FC042166881CB79B1598239CC0BEB89FCD17F
Name: 720p.mp4
Size: 1415857942 bytes (1350 MiB)
SHA256: 1BDF0EC85657EC432FC37327063D38D409763AEDECF6DB5AE8A32D4C5C503888
Name: 1080p.mp4
Size: 3070245483 bytes (2928 MiB)
SHA256: F6044C8A0454D7F0B6106E48D87982ED06278B89C0CDA79B5F854D63CD911A1A
Name: dvd.mp4
Size: 708157105 bytes (675 MiB)
SHA256: 09AE4CA32B43BB4F6683570160C2C36AAECBA318AB0959F50360A3232724519B