I don't understand what you try to say about articles meaning opposite things in both languages but you are mistaken. Please read about the articles in the "Tips and notes" of chapter "Basics 1" (website). La raggaza mangia l'uovo = The girl eats the egg. La raggaza mangia un uovo = The girl eats an egg. BTW the girls eat = le ragazze mangiano.
Some helpful links read in other discussion to make the confusion even bigger ;-) : https://forum.duolingo.com/comment/1012366 and https://italian.stackexchange.com/questions/2013/why-is-the-il-or-la-used-everywhere
When I click on the sound icon in the discussion it works, but when I click on the sound icon in the exercise itself, the sound does not work. This has been happening with all the exercises I have done in the food section during this lesson. Is anyone else having this problem of no sound?
No, it makes a difference. There are some grammatical errors that have become so common that they are generally accepted as correct, like saying "It's me" instead of "It is I". But, errors in conjugating verbs is not one of them. If you don't conjugate verbs correctly, it sticks out as being incorrect. Duolingo counts mistakes as typos only if the mistake does not create another proper word. You seem to speak English very well.