Complex sentence: Nuvolari drove for the Auto Union team for this race as he wasn't impressed with the new Alfa, however the tricky rear-engined Auto Union was not a car to race without some practice, even for a man of Nuvolari's skill.
Split into simpler sentences: Nuvolari drove for the Auto Union team for this race as he wasn't impressed with the new Alfa. However, the tricky rear-engined Auto Union was not a car to race without some practice, even for a man of Nuvolari's skill.