Back before level 2 was updated, there was a lesson on partative articles (when you want “some” or “a part of” something. According to my notes there are a few ways to say this, but there was a handy table on combining “di + definite article” that I can't find now.
Interestingly, when I search the terms from the table, like “degli”, audio clips show up in the “Lessons” section, but under no particular lesson!
Similar charts show up in lesson 9.8 on prepositions, using di, da, a, in and su, but it doesn't look like there's any practice in the course on partative articles now. I understand why the extra vocabulary lessons were removed as they didn't add much that wasn't in the audio lessons, but this seems like a worthwhile grammar lesson to me.