How are some people so good in English?

Aw. I completely understand how you feel because I, too, suffered from an English rut back in the day. Sadly, I had a friend from Poland who transfered to my high school at 14 years old and outscored me, a USA born citizen, in English! My advice to you is to embrace your jealousy. Jealousy is very motivating, and that raw emotion pushes you to write better and read more. Now, I can take on pretty much any pompous jerk in English. Since spending my 10th grade summer reading a book a day of the clics, I have never received an English test score below an A. Additionally, you need to pay attention to the way you phrase sentences. I understand that punctuation is a big deal, however, you will find in later years that Professors care more about content. In fact, the general public cares more about content. Tailor your essays into mature-sounding and concise flowing paragraphs. Maybe I am being elusive, but that is the nature of writers (I am teasing).