> I'm very impressed that anyone who speaks another language natively can get good at it.

From my completely anecdotal observations, native speakers are the worst at English. They struggle with homophones, prepositions, tenses, confuse meanings of words, apostrophes and I could go on and on.

English grammar is easier to learn by reading and writing than speaking, what most native speakers do.

Its/it's, they/their/they're, who's/whose, prepositions like a lot, a while and confused words like definitely and defiantly are the first that come to mind. See if you are better than a foreigner.