Original sentence: Historically an important seaport since medieval times and subsequently a principal ship-building centre, Gdańsk was a member of the Hanseatic League
Edited sentence: Historically an important, ethnic German, seaport since medieval times and subsequently a principal ship-building centre, Gdańsk (then known as Dantzik and Danzig) was a member of the Hanseatic League.Since 1945 Gdańsk has been part of Poland