While Samsung hasn't officially announced an Oreo update for the Galaxy J2 SM-J200G, developers have created custom ROMs that allow users to experience Android Oreo on their devices. These custom ROMs are built using the Android Open Source Project (AOSP) and are not officially supported by Samsung.
. However, the later "Core" and "Pro" versions of the J2 did feature Oreo (Go Edition), which may be the source of your performance comparison.
If you're interested in installing Android Oreo on your Galaxy J2 SM-J200G, here are some recommended resources:
Attempting to force Android Oreo onto an SM-J200G using unofficial methods involves significant risks: android oreo for galaxy j2 smj200g better
