To Downgrade from Android Oreo to Nougat OS, You must check our new article on How to Downgrade Galaxy A5 2017 from Android 8.0 Oreo to Nougat.
In this post i will guide you on How To Downgrade Galaxy A5 2017 A520F From Android Nougat To Marshmallow (Rollback). Earlier Samsung had released Android Nougat for Galaxy A5 2017 A520F . Check this link if you want to upgrade to Android Nougat (May Security Patch Build). In case if you didn’t like the update, you can revert to lower version anytime.
Android 7.0 Nougat comes with handful of features such as App Shortcuts, Multi Window support, restart setting to power menu, Launch the camera by pressing the power button twice, Image Keyboard support, 100 emoji added, GIF Support, Quick Reply via Notification, Notification Redesigned panel, Notifications prioritization, Enhanced Doze Mode, System UI Tuner, Customizable Quick Settings, Don Not Disturb, New Settings Panel Redesigned, Data Saver per App, seamless updates and New Emoji Support.
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Now you can easily revert back to Android Marshmallow using this guide. The Guide is simple and easy to return to Marshmallow from Nougat. Follow the steps which can change back to Marshmallow by download and flashing using ODIN software.

Thanks Buddy, it works
I’m trying downgrade with other firmware but odin fail, and try using pit file but odin fail again, then i find this post, i was try this at home, but i download firmware using SAMFIRM with code MAT (Marocco) , After download finished I flash my phone again but odin dont says fail, oh thankyou very much buddy.