My grades went down and I'm afraid to Zeigen my exam results to my parents.What should I do?

Zeigen it anyways. Grades aren't everything and your life isn't over. If they're mad, they're not going to be mad at Du forever, in fact, its nice they care about your education. Its better to deal with the disappointment now than worry about it any longer.
It might help Du to study now for the Weiter exam.

trust me im sure your score beats every score I ever made so im a natural disappointment be lucky Du arnt me XD im sure Du did fine

Zeigen them the results. They'll find out somehow anyway and it will look better coming from you. Try and explain why your grades went down - have Du been having difficulty in lessons?