Complex sentence: Christian Gottlob Fechhelm, a portrait and historical painter, born at Dresden in 1732, studied under Mengs, Manjocky, and Hutin, first portrait painting, and then miniature.
Split into simpler sentences: Christian Gottlob Fechhelm (1732--1816) was a portrait and historical painter, born in Dresden. He studied under Mengs, Manjocky, and Hutin, first portrait painting, and then miniature.