Thanks....already done, but it doesn't work. As advised above in this thread, i've downloaded the two apk of the Play Store and Play Services. Moreover I've added these apps to the Titanium backup. My idea is to not flash any zip for the gapps, then restore manually only the Store and the Services.try opengapps pico
go to opengapps.org then arm - 5.1 - pico and download and then, flash.
When I have a moment, I'll do it.