You don't have to start over, you can back up your saves. Go to Android/data/com.zimon.championofrealms/files and there will be a folder with saves. Copy the save somewhere save, uninstall the old version, and then install the new version. finally, put your saves back.
Some people have to do this because of the update to renpy. Ever since renpy 7.3.5 broke for all android builds its been a cluster, but hopefully 7.4.6 is stable enough that Zim doesn't have to upgrade it anymore.