Hi, unfortunately we don't currently have a built in method for backup/restoring Blockfolio, it's definitely something we intend to add in the future. However, an alternative that's worked for some users are apps such as Helium or Titanium Backup which allow you to copy the app onto a new device, so that might be an option worth exploring.  You might have to manually re-enable App permissions manually in Android settings if you go this route.

Helium : https://play.google.com/store/apps/details?id=com.koushikdutta.backup&hl=en
Titanium Backup : https://play.google.com/store/apps/details?id=com.keramidas.TitaniumBackup&hl=en