- go to your device Settings
- select "Apps"
- tap the three dots in the upper right corner
- select "Special access" or "Special permissions" (the translation differs among various phones)
- select "Paint over other apps" and allow
- now it should be possible to finish the setup
Further allow the "Dropzone":
- open the "Phone manager" app (on tablet it could be "Tablet manager" or "Device manager" - basically it is the spot where you may clean memory etc)
- slide right and there should be the "Dropzone management"
- allow the Avast Mobile Security app to "show Dropzone"