Complex sentence: The story centers on the life and work of the (fictitious) composer Adrian Leverkühn; his extraordinary intellect and creativity as a young man mark him as destined for success, but Leverkühn desires true greatness.
Split into simpler sentences: The story centers on the life and work of the (fictitious) composer Adrian Leverkühn. Leverkühn's extraordinary intellect and creativity as a young man mark him as destined for success, but his ambition is for true greatness.