Translation:I am eating hamburger and potatoes.
Navajo allows some distinction between habitual present and progressive present (see imperfective /progressive /iterative /usitative modes), but the weird thing here is that in some sentences Duo expects "eat" some others "be eating" and yet in some others accepts both (when all these forms are just imperfectives).
As I'm not expecting Duolingo to tackle on the difference between these 4 modes any time soon, I guess these discrepancies are more teething issues than actual grammatical distinctions.
I haven't a clue either, as the tenses and aspects haven't been taught yet. IMO, both "I eat" and "I am eating" ought to be accepted because of this.
To say in English 'I'm eating hamburger...' rather than 'a hamburger' or 'hamburgers' strikes me as very unusual, unless we mean just hamburger meat, which as a substance is uncountable, instead of being made into countable hamburgers. In that case, I would be more inclined to say 'ground beef' instead of 'hamburger.'