Board Thread:Shadow Fight 2 Discussion/@comment-26958678-20150912111526/@comment-25669516-20161105095141

It means your deice is not rooted. You must use an app like Kingroot, Towelroot etc in order to root your device first. Rooting voids device warranty so be careful though.

If you don't want to root your device you can also try out the Helium Backup app from Play Store. However it only works on a certain device models so you'll have to check your device compatiblity.