Complex sentence: In Hamburg, Emil had taken an apartment, but soon brought his mother from Vienna, and gave it over to her, while he moved in with Hel Braun in an apartment in the same neighborhood.
Split into simpler sentences: In Hamburg, Emil had taken an apartment, but soon gave it over to his mother whom he had brought from Vienna to live near him in Hamburg. He in turn moved in with Hel Braun into an apartment in the same neighborhood.