Hey mate, Raus here, from Shelter VN. For some reason you left exactly the same question in my comments section, so I'm gonna delete it there and answer here :P
Also, weird, didn't you already ask exactly the same question under Extracurricular Activities 230 days ago?
Anyway, if you're on android, just run the new apk and you'll have an option to update the build.
If you're on Windows or Mac, it's actually harder to LOSE progress than to keep it lol. Just download and unpack the game. All of your progress will already be there, Just try it.
I hope it'll stick this time ;)