Complex sentence: He reportedly stole some magical documents and Freemason scriptures of Duke Von Holstein-Gottorp during the Seven Years' War and learned more about magic from a merchant in Frankfurt am Main, who also supported him financially and brought him into contact with Freemasons in Braunschweig.
Split into simpler sentences: He reportedly stole some magical documents and Freemason scriptures of Duke Von Holstein-Gottorp during the Seven Years' War. He learned more about magic from a merchant in Frankfurt am Main, who also supported him financially and brought him into contact with Freemasons in Braunschweig.