If you want a direct, very aggressive translation , here are a few natural German options depending on nuance:

Blunt / Very offensive

  • „Was ist das für eine dumme Scheiße, die du da machst?“
    (Closest overall match; harsh and insulting.)

Slightly more explicit / stronger insult

  • „Was soll dieser dumme, beschissene Mist, den du da machst?“
    (Adds more intensity; “beschissen” ≈ “fucking”.)

More confrontational tone

  • „Was zur Hölle ist das für ein dummer Scheiß, den du da produzierst?“
    (A bit more expressive, still rude.)

Notes on tone

  • German stacks insults differently than English, so repeating multiple profanity words (“stupid fucking shit”) is usually compressed into phrases like „dummer Scheiß“ or „beschissener Mist“.
  • All of these are rude and confrontational , and could easily start an argument.

If you want, I can tone it down or make it sound sarcastic instead of outright aggressive.