Welcome to Android Forums mandem_Idn. Your newly purchased Samsung GT-i9508 Galaxy S4 Duos
running the Chinese version of Android 4.2.2 is not on the list of supported devices
for the Google Play Store app. Google does have a help site for the Google Play Store app
which says "If your Android phone or tablet is not supported for use with Google Play, or if after rebooting you still don't see the Google Play Store app, contact the carrier or manufacturer of your device. At this time, we do not offer a copy of the Google Play Store app for download." Wish I had a better answer for you. Don't lose hope though. You can still download paid android apps through Amazon.com
in their appstore.
Try a factory reset anyway though. This will restore your phone to the pristine state it was when it left the factory. There should be a Google Play store app on Chinese ROM phones but it is limited to only free apps.