if you didn’t liked the new version of android, you can easily rollback your Huawei p9 lite VNS-L22 from nougat to marshmallow by following the guide given below.

Instructions

• Your phone must have stock recovery (No TWRP)
• Must not be rooted.
• Backup all important data.
• Download downgrade package from this link: VNS-L22C900B300
• Make dload folder on your sd card
• Extract downloaded file and copy update.app to dload folder.
  Disconnect from PC
• Switch off your phone and use 3 buttons method to star update (Volume up, Volume down, power) keep them holding until update started
• Once process finished, check in about phone if it is showing VNS-L22C900B300. if its correct.
• Then download Marshmallow from THIS LINK and install same way you did earlier for rollback.
• Enjoy using Marshmallow.