Haha! I wrote "above all" because that was the translation of soprattutto in a previous sentence, and now it's supposed to be "mostly". Anyway I never cook desserts, I make them. And cooking "sweets" sounds rather bizarre to me, somewhat like cooking candy.
As a British person commented earlier, dinner is called tea in England - and they also call dessert pudding. No wonder we're surrounded by puzzles here. Linguistics and semantics are truly wondrous things :-)
Should it be acceptable to write ' i cook mostly sweet things'? I think there is an ambiguity around the word dolci (see conversations below) that includes all these sweet foodstuffs
In America we don't "cook" sweets or desserts - one bakes baked goods, or probably makes candies/chocolates/other confections. I've never heard anyone say they "cook" these items
In the UK, or at least when i was growing up, 'sweet' can mean any type of desert.
Why Duolingo does not give translation tips as "mainly" and "mostly" if these are two and only acceptable translations for this sentence?
"I cook mostly sweet things" should be accepted. As others have pointed out, you don't cook sweets.
I cook above all sweets, does not make sense in English, I mainly cook sweet things would be better.