Hiya

I need the English term for routines that look like the trick gone be wrong but suddenly there is a surprising, unexpected end.

In German it's "Aufsitzer Trick"

The term you're looking for might be "sucker trick." A typical plot will have the audience believing they've discovered the secret, or believing the magician will fail. In the climax, it is revealed that the audience did not really know the secret, or that the magician has not failed.

I've also heard this described as "magician in trouble" or "magician in peril."

Doug's answer is probably what you are looking for, but there are other approaches that are close that you might consider.

"Spectator as hero," "garden path," "thematic interlude," and even "false premise."

PM me if any of these are of interest, or ignore if Doug's answer is complete enough.

Literally between your German and English would be a "Flop" Trick, but I think it probably hints at "Flip-Flop" Trick. The English idiom "Flop" means to fail or unsuccessful, so a "Flip-Flop" would mean to "make an abrupt reversal of failure".
(Just to beat a Dead Horse! haha)

Thank you for your help.

I try to construct a routine as an example.
A spectator picks a card. After a few shuffles and some mambo jambo I try to find his card in the deck. And I fail, lets say 3 times, I shrough and turn around pretending walking away. On the back of my jacket is a big card showing the value the spectator picked.

Hope it explains what kind of effect I'm talking about.

Greets
El

Tommy Wonder called them "failureffects" (Books of Wonder Vol. 1). It seems that the term has not been widely accepted by the magic community. The general thinking is (extremely abbreviated) that "sucker trick" shows a lack of respect for the spectators, while "failureffects" just describes the presentational effect of failed attempts before the successful climax.