Complex sentence: István Avar (28 May 1905--15 October 1977) was a ethnically Romanian footballer of German descent and a legend of Újpest FC, most famous for playing for the Hungarian national team in the 1934 World Cup.
Split into simpler sentences: István Avar (28 May 1905--15 October 1977) was footballer of German descent who at various times competed for both Hungary and Romanian. He played for Újpest FC, most famous for playing for the Hungarian national team in the 1934 World Cup.