Complex sentence: Erik Brandt's father had emigrated from Germany to Denmark in 1939 and started the firm of "Brandt og Salling", he was not Jewish, but had had a thriving clothing business with many Jews in Germany.
Split into simpler sentences: Erik Brandt's father had emigrated from Germany to Denmark in 1939 and started the firm of "Brandt og Salling". He was not Jewish, but had had a thriving clothing business with many Jews in Germany.