If you spoke nothing but German one day to your English-speaking friends and co-workers, it would probably result in complete bewilderment. Bewilderment is a state of being confused and puzzled.
Bewilderment means not understanding, but it goes beyond that — it implies a state of complete mystification. People experience bewilderment when they are utterly baffled by the situation at hand. The word is a relatively new one, first recorded in the 1680s as a combination of be, "thoroughly," and wilder, "lead astray or lure into the wilds." You can think of bewilderment as being led into the wilderness and left to puzzle your way out.