Simplify the following text for a Grade 15 native English-speaking person.
Original: At the opening of the new Reichstag on 21 March 1933 , at the Kroll Opera House , the Nazis staged an elaborate ceremony , in which Hindenburg played the leading part , appearing alongside Hitler during the event , that was meant to mark the continuity between the old Prussian-German tradition and the new Nazi state .
Simplified: At the opening of the new Reichstag on 21 March 1933 , at the Kroll Opera House , the Nazis staged an elaborate ceremony , in which Hindenburg played the leading part , that was meant to mark the continuity between the Prussian-German tradition and the new Nazi state .