Complex sentence: In 1901 his sole opera "Manru" received the world premiere at Dresden, then it had American premiere in 1902 at the Metropolitan Opera and to this day remains the only Polish opera by a Polish composer ever performed there.
Split into simpler sentences: In 1901 his sole opera "Manru" received its world premiere at Dresden, then it had its American premiere in 1902 at the Metropolitan Opera. To this day it remains the only Polish opera by a Polish composer ever performed there.