This happens only with android 6+ Is there any way for my app to check if you have Storage Permission and if not to ask you this permission with a message?
Set targetsdk to 22 or lower. Starting from 23 you need to use Runtimepermission.
Once request4ed the Permission you dont need to answer again. Even after a update.
Deinstalling the app will remove the permission too. So if you install it again you need to anwer the permission once the app is started.
See Runtimepermission Tutorial about more informations...