Maybe they should look for an editor who is a native speaker, though. The language here is super stiff and formal regardless of who's speaking, and contains mistakes on almost every page. Here are some of the obvious ones I've noticed (not listing all instances of awkward phrasing here):
"But it's probably dangerous if it was for the past us" (-> it would probably be challenging for the past us)
"I have to reconsider about the special lesson" (-> reconsider the)
"So smoothly like this" (choose one)
"So suddenly like this" (choose one)
"I won't accept it before I hear it directly from his mouth" (-> until, from him)
"Even though it's temporary, but I have been entrusted" (choose one)
I mean it's clear that even if they have someone who's supposed to check these lines for correct English (which I doubt), that person doesn't really know what correct English looks like.