The same happens with the skill names

Hey, so sorry to leave you waiting for this long without a response. I am unfortunately only a native english speaker, and the issue you are having is with the mods Localization file, as your game is not in english, but what I assume is your own first language. This means any time a name associated with the class would appear in your game, a Blue String will appear instead of normal text. The only way to fix this is for me to add a localization for other languages, but I can't make any of them myself.

I apologize and should have included a disclaimer in the mod itself that it only displays properly in English Games. The Class will function completely mechanically even with those Blue Strings, so if you are willing to put up with it, he does still work and is usable.