change bottom margin to 25mm

lecture.cls

@@ -27,6 +27,10 @@
 
 \usetikzlibrary{quotes, angles}
 
+\geometry{
+    bottom=25mm
+}
+
 %\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
 \DeclareOption{uebung}{
     \makeatletter