I also don't speak English well, so reading takes some time)))) On average it takes around 30-45 minutes for the one day of the route. So it will take 20 hours per character and 150 hours for the whole game.
This game has become so big that when you try to extract only dialogues into one Word document, sometimes it crashes 
. I'm working with the .146 version and there are almost 2,000,000 words already! This VN definitely deserve place in the gaming hall of fame.