Complex sentence: The polling stations are opened on Saturdays and Sunday mornings but most people vote by post in advance ("Abstimmungssonntag" in German); at noon on that day, voting ends and the results are usually known at the end of the afternoon.
Split into simpler sentences: The polling stations are opened on Saturdays and Sunday mornings but most people vote by post in advance ("Abstimmungssonntag" in German). At noon on Sunday, voting ends and the results are usually known at the end of the afternoon.