After the firmware update on Android Nougat it is possible that your Samsung Galaxy S7 pictures, which are displayed in the gallery, are automatically synchronized with the Samsung Cloud. This setting was active at least on our test device after the Android 7 update!
Synchronization with the Samsung Cloud is perhaps not desirable and so we now explain how to disable it:
1. Open the gallery app on the Samsung Galaxy S7 (Android Nougat)
2. In the top-right corner of the album, tap the three-point icon and select Settings from the menu
3. Right at the top you see "Cloud Synchronization". Disable this option by setting the sled to "inactive"
From now on, pictures in the gallery of your Samsung Galaxy S7 are no longer automatically synchronized with the Samsung Cloud, which is our opinion is more pleasant.