Complex sentence: The old man gives the three tasks that would lift the enchantment from the castle, but only Witling is able to succeed, because the animals that Witling saves help him gather the thousand pearls, the key to the Princesses Room and which princess to choose.
Split into simpler sentences: The old man gave the three tasks that would lift the enchantment from the castle, but only Witling was able to succeed. This was because the animals that Witling saved helped him gather the thousand pearls, the key to the Princesses Room and which princess to choose.