tbh, I don't mind a slow update.. so if people can't wait they can buy the official instead (Vol 2-4) to support author as well (to avoid getting axed).
I think its also a good idea to put a message at the banner in every chapter in the future to encourgae people buying Vol 2-4 in amazon. So not only mangadex's user, it can also encourage people reading from another sites who copy chapters from mangadex