If you can copy the save folder from your game (inside www folder) and put it in the "www" folder (replacing the old save folder there) of the new downloaded and unzipped version, and do the step 5 of the installation again with the new version ( https://itch.io/t/3569182/play-on-android-with-joiplay ), it might work? I haven't tried this, but logically it could work.
