Downsizing texture assets from Marketplace

If i export ‘EuropeanCrossbow_NRM’ as tga i get this warning

and the exported texture looks like this which is wrong

Also when i try to export ‘EuropeanCrossbow_RGS’ i can’t export to any readable format

Any way to properly export those assets? If I compress them in-editor then it doesn’t fix my high space usage problem or editing them.