Who was
gathering of free Germanic men to make a decision

During the Viking Age, the Norse had an oral culture and only rune writing existed. However, the Vikings had both law and government even without written law. All free men of the Vikings would gather in their communities to make law and to decide cases in a meeting called a Thing.

Explanation:

this is what i learned in school so maybe it will help you

where is the diagram

its many islands, high mountains, and remote peninsulas isolated population centers.