Complex sentence: After Frederick the Great's death the prince-bishop Krasicki continued friendly relations with the Prussian king and in 1795, six years before his death, Krasicki was elevated to Archbishop of Gniezno (thus, to Primate of Poland).
Split into simpler sentences: After Frederick the Great's death, Krasicki continued friendly relations with Frederick's successor. In 1795, six years before his death, Krasicki was elevated to Archbishop of Gniezno (thus, to Primate of Poland).