well i downloaded the new version of the game and it doesn't seem like I can start from my save data back in the previous version, soo I'm wondering either I don't know what to do or I have to start over
Ah, ok, I see!!
Technically, overwriting the new files in your previous folder should be enough
Since your save files are inside the folder www/save
You should have these files:
If you have only the last one of this list it means you lost your data, but if you just copy the new version files into the folder where you have the version 0.3.4 these should not be affected in any way