Was Kristallnacht the first act against the Jews in Germany in the time before WWII?
Kristallnacht was not the first act against the Jews in Germany.
Depending on what you call an "act," acts against the Jews had been occurring even before the Nazis took power. The Nazis attacked Jews vebally through propaganda and, to some extent, physically through the "brownshirts" or SA.
Once the Nazis came to power, they started to make laws limiting the rights of Jews. These are what I would call the first act against Jews. They started in 1933 with a variety of laws limiting the sorts of jobs that Jews were allowed to hold. They then continued with the infamous Nuremberg laws that stripped Jews of their status as German citizens. This was in 1935. Kristallnacht did not happen until 1938, meaning that it was not the first action against Jews. It might be said to have been the most violent and destructive up to that time, but it was not the first.