Honor 5c (NEM-L51): back to Marshmallow?

[Guest Voxpop2011]

Since upgrading to Nougat only very recently, the phone battery is draining fast and some of the functionality of Marshmallow is gone.  Some of the irritations may seem minor to power users, but I am a low grade user - a bit of email (the unified inbox drives me mad) - messaging/calls mostly via WhatsApp and some internet use.

I have not rooted, so no custom roms. Can I go back to Marshmallow from Nougat and, if so, does anyone have the stock rom?  I would also appreciate an 'idiot's guide'.

Thanks

Edited November 7, 2018 by Voxpop2011
No-one? In fact, I managed to find a handset still running Marshmallow, but I would still like to roll back from Nougat.