Marlene Dietrich wrote the plot outline in an attempt to broaden her exotic appeal. She's still a cabaret singer. And she meets her husband (Herbert Marshall) while she's swimming naked in a lake in Germany... but then the narrative diverts towards a more conventional Hollywood soap with the star suffering poverty and disgrace while struggling to provide for their son alone.
The best (and most famous) scene is a nightclub routine with Marlene in a gorilla costume. She removes the disguise to sing the excellent 'Hot Voodoo'. But the glamour and the naturalism clash. Dietrich complained the box office was undermined by censorship and it's possible to imagine her descent into the gutter may have been planned as more realistically brutal.
Josef von Sternberg wasn't a director for social realism though. When his star is compelled to live in a flophouse, he creates the most beautifully lit flophouse in cinema. The milieu is exotically sleazy. Marlene does a lot more acting than usual, rather than a model for von Sternberg's adoring lens.
Pre-stardom Cary Grant plays an unlikely gangster! Sidney Toler is fine in a cameo as a sordid detective. It's a curiosity. No one else walks on the wild side with Marlene's insouciance, but it just doesn't compute when she’s forced to wash dishes. That's what Lillian Gish does in a Griffith film, not Dietrich in a von Sternberg. It's an interesting diversion but only intermittently successful.