Complex sentence: From 1990 to 1998, he taught at the Schule für Gestaltung (School for Design) in Basel, and from 1999, he taught German and philosophy at the grammar school in Muttenz.
Split into simpler sentences: From 1990 to 1998, he taught at the Schule für Gestaltung (School for Design) in Basel. In 1999, he started teaching German and philosophy at the grammar school in Muttenz.