A new update has started hitting the Samsung Galaxy A5 (2016) and A7 (2016). Weighing in at just under 40MB and currently hitting units in India, it's a security update that brings Android fixes for the month of June.
Given the size, it's reasonable to assume that no major feature is included the in the update, although the change-log does say that a "critical security vulnerability" has been patched.
Given that it's an OTA roll out, it might take some time for the update to hit your device. Meanwhile, if you feel impatient, you can manually check for it by heading to your handset's Settings menu.
If your chinese phones get updates it's obviously a high-end or mid ranger, nobody update low-end devices.
Who give a fk about your Galaxy Core, it's not a flagship nor mid-ranger, and it's old, stay in the past.
Your right about the Samsung update been poor. My last Samsung device was the Galaxy Core. The phone though hard a capable hardware, never got any update beyond the Android jellybean 4.1.2, not even Android 4.2. Since then, i had dropped their phones...