In his youth, he studied with Jesuits in that city and later at the Collegium Germanicum in Rome, which was also run by the Society of Jesus.
On July 30, 1668, he was elected Archbishop of Salzburg and received the pallium on December 8 of the same year, the feast day of the Immaculately Conceived Virgin Mary; on the same feast day, he was appointed Bishop of Lavant, a suffragan bishopric of Salzburg.
On September 2, 1686, he was elevated to cardinal by Pope Innocent XI; less than a year later, the chief shepherd of Salzburg died.
[3] Gandolf initiated various measures in the spirit of the Counter-Reformation: he founded the Seekirchen Abbey (1679), had the original pilgrimage church in Maria Plain built, established the court library, founded the Augustinian monastery in Hallein, and initiated the All Saints' Church in Tittmoning as well as the Theatine monastery in Salzburg.
His remains were buried in a pewter coffin in the crypt of Salzburg Cathedral, while his heart and entrails were taken to the Maria Plain basilica.