Hi,
To update google play store try any of these methodes.
Step 1,
open google play store>menu>settings>scroll down to,
build version tap on this,
google play store update automatically, let it finish,
when it finished,
reboot/restart device.
Step 2,
settings>storage>apps> google play store>
tap on uninstall updates.
Leave the device with sufficiently charged battery and connected to stable WIFI/WLAN.
Google play store update automatically.
Let it finished.
reboot/restart device.
Step 3,
open the link below.
http://www.apkmirror.com/apk/google-inc/google-play-store/
From here select last version of the
Google play store and tap on it.
See next play store icon , tap on the google play store icon.
Google play store update automatically.
Let it finished.
Still it is not update
Go to settings>security>scroll down to
" unknown sources " tap here a warning
pop-up comes tap on OK button(check).
Now open the link below.
http://www.apkmirror.com/apk/google-inc/google-play-store/
From here select last version of the
Google play store and tap on it.
deselect the play store icon.
Scroll down to download icon.
tap on the download icon.
a warning pop-up comes tap on OK .
When the downloaded is going on.
Go to settings>storage>downloads
Tap here and see the downloading link.
After downloading finished,
Tap on the link >install>tap here,
finally tap on the "done" button.
Play store is updated to the latest version.
now return settings>>>>unknown sources,
"uncheck" in the box next to this.
reboot/restart device
https://goo.gl/photos/M4UcnUxLPLBWvATh8