You only kept one savefile? This is just one reason why you shouldn't do that.
I have a few ideas on how to recover your progress but they wouldn't work on Android. If you can get your save working on a PC version of the game then reply to me and I'll write up the instructions for you.
Otherwise, you can either play from the beginning, which people often do, or use mods that let you start at a chapter of your choosing.
Okay, I made a mod that is primarily a walkthrough mod but can also let you start from any chapter. Install it, tap the big N on the title screen five times and follow the instructions. Afterwards, if you want to play without any help, you can disable the mod in the settings or uninstall it again.
Uhm, you have to find to the folder where you moved the archive.rpa file into when you installed Eternum, which is the same folder you also moved my mod file into.:"Documents/Ixalon/com.caribdis.eternum/game" And then you just move the new archive.rpa file, which was included in the most recent game download, into it. Your phone might ask you to confirm the overwrite and that's it.
