Complex sentence: Beren was a mortal man on the run from the Dark Lord Morgothand an outlaw and whereas Lúthien had lived for tens of thousands of years in the world, Beren was young even by human standards.
Split into simpler sentences: Beren was a mortal man on the run from the Dark Lord Morgothand an outlaw. Whereas Lúthien had lived for tens of thousands of years Beren was young even by human standards.