Complex sentence: After distinguishing himself as a promising and imaginative student and finishing his education, he left Russia for Rome where he worked until 1835 as a portraitist and genre painter, though his fame as an artist came when he began doing historical painting.
Split into simpler sentences: After distinguishing himself as a promising and imaginative student and finishing his education, he left Russia for Rome. Here he worked until 1835 as a portraitist and genre painter, though his fame as an artist came when he got involved in historical painting.