European variant of Huawei P9 Plus came with single sim functionality and Chinese variant doesn’t have playstore in it. you can enable dual sim function and you can have playstore by re branding it to Middle Eastern /Asian region. This guide is applicable to devices running marshmallow.

Rebranding Guide: 

• Backup all important data from your phone
• Enable OEM unlock in developer options
• Unlock bootloader of your phone (How to unlock?)
• Enable USB debugging
• Download SRKtool from THIS LINK (credit somboons from Thailand)
• Extract SRKtool zip file
• Open SRKtool and install TWRP recovery by selecting option 3
• Follow instructions on screen to complete TWRP Installation
• Then again select option number 4 to root your phone
• Once phone rooted, Select option number 7
• On next screen chose 9, Then on next screen chose 4 (P9 Plus)
• On next screen choose which region you want on your phone. (C185 is Middle East, C636 is asian)
• You will get root access prompt on phone screen, which you have to allow.
• Once OEM info changes successfully
• Download Marshmallow which matches your new regional files.
• Install stock recovery by choosing option 4 in SRK tool
• Then copy dload folder from firmware zip file to your sd card
• Switch off phone and hold all button, keep holding until update starts

For more details and Guidance you can watch following video tutorial