Simplify the following text for a Grade 10 native English-speaking person.
Original: He is most famous for his operettas â `` the most successful of which is The Merry Widow ( Die lustige Witwe ) â `` but he also wrote sonatas , symphonic poems , marches , and a number of waltzes ( the most popular being Gold und Silber , composed for Princess Pauline von Metternich 's `` Gold and Silver '' Ball , January 1902 ) , some of which were drawn from his famous operettas .
Simplified: The best known one is The Merry Widow ( in German : Die lustige Witwe ) which is probably the most popular of all operettas . He also wrote sonatas , symphonic poems , marches , and a number of waltzes , some of which come from his famous operettas .