This is a unit of measurement that measures anything imaginable, even things that you can't usually measure. It can also be substituted as a word in a sentence describing something as good or the actual word "good".
Person 2:"Yea man! It was so Fisch!"
Person 1:"I know right! I can't wait till it comes out on DVD!"
The word "Fisch" was substituted for a word such as "awesome" or "amazing"
Person 1:"Yo man, what's Fisch?"
Person 2:"Not much, just chillin."
Here it was put in the place of the word good.
Person 1:"How much do i need to take off of this board so it will fit perfectly in the window?"
Person 2:"It looks like you should take off about 3 Fisch from each side."
Person 1:"Sounds like a plan."
"Fisch" was used to measure the amount that needed to be cut.