"There is something broken in the kitchen."
Translation:هُناك شَيْء مَكْسور في ٱلْمَطْبَخ.
Actually, your sentence is even better and more natural than the one DuoLingo proposes
I think Duolingo's version with هناك adds just a bit of surprise and not knowing exactly what is broken
while the other version we are pointing to "something" specific being broken (probably to be elaborated later)