i just realized how badly explained my fix is ^^'
so to make things clear:
the simplest way is to just reinstall your game in english.
the slightly less simple way is as follows:
- open your current save with the texteditor of your choice
- at the bottom of the file are the kerbal-configs. Find all Kerbals with non-english trait identifier an substitute them with the correct english trait identifier (for Pilots: trait = Pilot, for Scientists trait = Scientist and for Engineers: trait = Engineer)
- save the file and load the save in KSP. You dont need to restart the game, just load the savegame.
- i guess, whenever you get a new Kerbal of the 3 standard classes, you have to rename his trait in the savefile.
i hope this is more of an instruction!