Complex sentence: His masterpiece was "The Moral Theology" (1748), which was approved by the Pope himself and was was born of Alphonsus' pastoral experience, his ability to respond to the practical questions posed by the faithful and his contact with their everyday problems.
Split into simpler sentences: His masterpiece was "The Moral Theology" (1748), which was approved by the Pope himself. This was born of Alphonsus' pastoral experience, his ability to respond to the practical questions posed by the faithful and from his contact with their everyday problems.