Complex sentence: Wehrlein began karting in 2003 and raced only in his native Germany in his early career, working his way up from the junior ranks to progress through to the KF2 category by 2009, when he finished on fifth position in ADAC Kart Masters.
Split into simpler sentences: Wehrlein began karting in 2003 and raced only in his native Germany in his early career. He worked his way up from the junior ranks to progress through to the KF2 category by 2009, when he finished on fifth position in ADAC Kart Masters.