"No, you are not a boy."
Translation:Ne, ty nejsi kluk.
Many native English speakers use incorrect grammar all the time. Many American's can't even read above the 3rd grade level. https://fee.org/articles/did-public-schools-really-improve-american-literacy/
50 percent of U.S. adults can’t read a book written at an eighth-grade level.
14% of adults can’t read anything. https://www.creditdonkey.com/illiteracy-in-america.html
There is little correlation between growing up speaking a language and speaking the language like an educated, or even literate, person.