Zeilenabstand

The German forum is over at https://musescore.org/de/forum/52 ;-), here a reply in English.

I guess you really mean system distance, not staff distance? For the latter that is a min and a max value you can tweak, for the former there is only one value, futhermore there is grand staff distance. You find them all at https://musescore.org/en/handbook/layout-and-formatting#style-edit-gene….

There's more to it though, including https://musescore.org/en/handbook/layout-and-formatting#layout-stretch and https://musescore.org/en/handbook/page-settings

google translation: How can I adjust the line spacing so that the piece fits on two pages?

First of all, there is a German forum where German speakers will help you, but since you asked here I will try to help you.

In the Style->General... menu dialog box you can change the staff distance and min. system distance. If this does not allow for your score to fit on 2 pages then you can go to the Layout->page settings... dialog and change the scaling a little at a time until the score fits on 2 pages.

The handbook is also translated to German. Here is the link to the German page that will help further explain how to adjust the score layout and formatting. https://musescore.org/de/handbuch#Formatierung