Grün finished his school years in 1964 with the A-level equivalent Abitur at the grammar school in Würzburg, Germany. In the same year he began as a novice at the nearby Benedictine Münsterschwarzach Abbey.
In 1964, Grün graduated from the grammar school in Würzburg, Germany with the A-level equivalent Abitur. That same year, he began his novitiate studies at the Benedictine Münsterschwarzach Abbey nearby.