You need to justify this. Where in the poem does she do it? Which lines are telling us about Nature's magnificence?The poetess describes the immense beauty of Nature by emphatizing its intensity and magnificence, which is in contrast with the human being who is so tiny and insignificant.
The word is "simplicity", even though it's "semplicita" in Italian.We can only admire “its semplicity” without saying a word because we cannot do this even if we want to.
Again, you need to justify this interpretation.We live in a world in which macrocosm and microcosm doesn't coincide as we are not part of this “semplicity”, which even nowadays is mostly incomprehensible.
The word is "mechanisms".We are inert observers who cannot explain neither the easiest meccanisms of the surrounding universe,nor describe properly her beauty.
Generally, your interpratation and analysis lacks analysis. You just said what you think the poem means. You didn't say why you think so. You didn't analyze the poetic devices used in the poem either.