Are you playing on browser? Save files are stored in cache, so if you are in incognito or your browser decides to clean up your cache, that can cause them to be wiped. You're best off just downloading the game onto your device and playing that way.
I did installed it! That's why i'm so confused why it erased everything
Check to see if the save files are there?
Windows: C:\users\(username)\AppData\Local\UserData\Default\Elf Jail
Mac: \Users\(username)\Library\Application Support\Default\Elf Jail
Linux: \Users\(username)\.config\KADOKAWA\RPGMV\Default\Elf Jail
