Hi I had the same issue, in the previous duolingo course اَلْأَكْل طَيِّب meant 'The food is good' but in this one اَلْأَكْل means 'eating'. Which was really confusing me, so I asked a couple of my Arab friends, they confused me even more, apparently food is طَعام and eating is يأَكْل or آكْل. So I do not really know what duolingo is teaching here, which makes me doubt everything else I've learned in Arabic on this app too.
I have heard other people say "أَكْل" means "eating" (and also "food" in some dialects. It is both a noun that means food and a verbal noun that means eating. In Arabic, they use a lot of verbal nouns (kind of like gerunds and participles in English), especially after conjugated verbs.