Complex sentence: Merlin spends some time learning magical skills from Frik (Martin Short), Mab's gnome sidekick, but he doesn't really like magic and eventually leaves for his old home when he learns that his foster mother Ambrosia is dying.
Split into simpler sentences: Merlin spends some time learning magical skills from Frik (Martin Short), Mab's gnome servant. He doesn't like magic and eventually leaves for his old home when he learns from Mab that his foster mother Ambrosia is dying.