They translate and upload the paid chapter that is only available on the app. I could also do that but it is against mangadex's policy if I remember correctly.
It's got an official English release on K-manga app. The chapters are available on other manga sites, but if you want to read the manga legally and support the series/author, consider reading it on the K MANGA app (US Only or use VPN).
It's got an official English release, so I won't be doing it anymore. You can read up to chapters 35+ on other manga websites. Or if you want to support the official release, you can read it on the K Manga app (US Only or just use VPN)
Fixed! And yes, you are correct to assume that the script segment overall is in modern standard Japanese as mentioned by Hinata in page 11 - "Itou-san has arranged the lines to make them easier to say".