Your English is good, don't worry on that score. My problem, as an American, was writing the stories using English english- getting their slang phrase and words right ( biscuits not cookies, jumper not sweater, trainers not tennis shoes ).
Just so you know what you're getting into,
'What goes around . . ."
"Having both is a blessing "
And
"Isn't not easy to explain, but . . "
Are as long as JKR's longest novels, so just try one, maybe two chapters a day or you'll go cross eyed ( just kidding )
Enjoy!!!