I have a Lumia 430 Dual-SIM with Windows Phone 8.1. After some research, I came across this site, but it only give details on how to log out using Android. I then thought of uninstalling Facebook Messenger and installing it again with the idea given on the site I mentioned, but the Store keeps showing me a "805a8011" error message which I was told to hard reset my phone to fix that, but I can't. I just have too many files to backup with little amount of internet bandwidth, meaning I'm currently using 2g network and my Spectranet is downloading at 145 kb/s.
In a nutshell, I thought of different alternatives that aren't actually in my favor, so the answer I'm expecting is one without resetting my phone but any other apart from that is welcomed.