Complex sentence: The Elector Frederick III established a university at Wittenberg in 1502, at which the Augustinian monk Martin Luther was made professor of philosophy in 1508; at the same time he became one of the preachers at the castle church of Wittenberg.
Split into simpler sentences: The Elector Frederick III established a university at Wittenberg in 1502. At the same time, he became one of the preachers at the castle church of Wittenberg.