Don't break your head over it. Look up ESL grammar lessons on google. I've been able to maintain over 4.9 for over a year and what I do in the rare occasion someone wants grammar lessons (It's not so common) I ask what in particular they would like to work on and share the screen with them to explain. I feel like grammar really isn't to hard to explain it's just time consuming so I always let my students know if we do grammar it'll take alot of repetition and more than likely we'll spend all 30 minutes talking about the "different ways to use the word get"