Simplify the following text for a Grade 5 native English-speaking person.
Original: Siegfried is the third of the four operas that comprise Der Ring des Nibelungen ( The Ring of the Nibelung ) , by Richard Wagner .
Simplified: Siegfried is an opera by Richard Wagner . It is the third of the four operas that together tell a story called Der Ring des Nibelungen ( The Ring of the Nibelung ) .