Duolingo is a great introduction for many things: tourist phrases, sentence structure, vocab, but there are hidden limitations you won’t find out until you step outside of Duolingo.
There are threads on Duolingo on here already so I won’t go through those pros and cons again lol (though, I do still use Duolingo).
The sentence regarding “my bento” uses “boku no obentou” instead of “watashi no bentou”.
Firstly, there are multiple versions of the masculine pronoun for “I”. Watashi is a polite, gender neutral term that would be acceptable and understood anywhere. There are others, such as “boku” or “ore” that convey different senses of casualness or masculinity.
In other words, even referring to yourself in Japanese is a minefield of nuance, expectation and projection (welcome to Japanese, it only gets more complicated from here!), and I understand why most people leave it out altogether!
Secondly, adding an “o” in front of something, like o-bentou or o-namae is a sign of respect. There are some words that are more common to have an “o” in front of.
As with most Japanese rules, you just get used to seeing it.
What I would do in your situation is not to rush anything. Go back through the N5 Lesson 1 reading exercises in detail. Read it, and listen to it, so you know what it sounds like. Make sure you know every word being used. Look them up in a dictionary, write them on a piece of paper, whatever works. Then I would write out the Japanese (either in romaji or hiragana), and try to understand what each word and particle is doing in the sentence.
Then once you’ve done that, have another read through and see if it makes more sense.
It will take ages. maybe an hour per scenario in the N5 L1 tab.
But this kind of exposure and repetition is invaluable. You are creating building blocks that will make it easier the next time you encounter these ones again, or you will know what to do next time you encounter something new and confusing.
Despite the “I speedran N1 in 12 months” youtube videos, learning Japanese is actually difficult, but I’ve found it’s more enjoyable if I take longer to understand what I am looking at.
Good luck!
