Complex sentence: His parents, Paul Karrer and Julie Lerch, were Swiss nationals and in 1892 the family returned to Switzerland where he was educated at Wildegg and at the grammar school in Lenzburg, Aarau, where he matriculated in 1908.
Split into simpler sentences: His parents, Paul Karrer and Julie Lerch, were Swiss nationals. In 1892 Karrer's family returned to Switzerland where he was educated at Wildegg and at the grammar school in Lenzburg, Aarau, where he matriculated in 1908.