"저는 이것을 먹습니다."
Translation:I eat this.
Is it how formal and rigid they sound? Would a different case help? Or is it just the phrasing?
What is the function of 을 in 이것을? Isn't 이것 by itself a word meaning "this" or "this one?"
을 is an ending used to mark the object; in this case, what is being eaten.
the function 을 is to turn the word it's referring to (이것 in this case) into accusative.
"I am eating this" is also correct, but Duolingo hasn't updated their answer set yet. It's in Beta still, just give it time. Many languages' present tense predicates can be translated into both present progressive and simple present in English. (cf. "Je mange des fruits" --> I am eating fruit/ I eat fruit)
Declaration. If by confirmation you mean "I do eat this." then it would be:
저는 이것을 먹기는 먹습니다.
What about translating this to, "I am eating this." since "I eat this" isn't really proper English.
There's no gerund in korean, they have modifiers particles. You can search about it if you want but I think you should learn the basic verbs first