Looks like the language (text) files are missing altogether. Weird how it happened on the Steam version. Either way, assuming you're running a clean install (no mods), try re-validating the game files - or whatever it's called - via the game library menu. It will take a while, I guess, but that's usually the first step you take when such problems occur.
If you`re unfamiliar with Steam and validation. Open Steam>Library and right click the witcher and select properties then in the new window click the local files tab and tick the verify game cache button. If the game is lacking any files Steam will notify you that is acquiring some files.