Complex sentence: Franz Matthias Hiernle erected left of the altar an epitaph for Georg August Samuel von Nassau-Idstein (1665--1721), his wife Henriette Dorothea and their children, designed by Maximilian von Welsch, who had also designed the interior of the Idstein castle.
Split into simpler sentences: Franz Matthias Hiernle erected to the left of the altar an epitaph for Georg August Samuel von Nassau-Idstein (1665--1721), his wife Henriette Dorothea and their children. The epitaph was designed by Maximilian von Welsch, who had also designed the interior of the Idstein castle.