Question permission denied

Hey, thanks for a great guide!
All steps went smoothly and for the most part my Tablet Z2 now appears to be rooted.
For instance MyBackup Pro, Tasker, Secure Settings, App Quarantine all work.
However, there are some apps that have issues and they complain about permission denied in /system folder.
Apps are
  • BusyBox (unable to install binaries),
  • SuperSU (I was able to install it from Play Store, but as soon as I start it it tries to update to latest version, which fails)
  • AdAway (fails to apply hosts file)

Any ideas?