There are still many smartphones running on Android Lollipop, but Samsung has been on an upgrade spree to Android Marshmallow. New in line it the 1st-gen Galaxy A7 which has now started getting its OTA Android 6.0 update.
There are a lot of improvements in store for you, including the new refined and cleaner TouchWiz interface with support for Google Now on Tap, Doze Mode and App permissions.
You can head into Settings->About phone and check for updates on your Galaxy A7 for the update if you haven't got a notification yet. SamMobile also points out that the first-gen Galaxy A5 would be next to get Marshmallow update, so we'll keep a lookout.