"I want something more to eat."
Translation:Minä haluan lisää syötävää.
Jotain may not be necessary but given the original statement included the word something and we were asked to translate. Whether or not it is necessary should not be the issue. Whether is it acceptable is the issue. If it could be considered acceptable, then marking it wrong is more of a discouragement and adds to confusion
I keep getting thrown off by the "something" in the English translations. I finally reported it by suggesting that they drop the "something" in the English part. That way the sentence should be "I want more to eat OR I want some more to eat (which sounds more unnatural to American English anyway)." Does anyone have feedback about that?
Syödä is an infinitive verb, specifically the first infinitive, short form. I've never seen a short first infinitive decline, so I don't think it can have the partitive ending added to make syödää.
You could make a sentence with syödä, but then jotain lisää would need to be the object of syödä, resulting in a word order more like Haluan syödä jotain lisää. However, this would be a better translation of "I want to eat something more", rather than "I want something more to eat".