So I've been using WP for a long time and i kept forgetting what setting i used. My host did a bunch of tuning, even had varnish etc, but it didn't help that the backend was slow.
Then i found out that, you just need to disable object caching on your caching plugin and they will speed up your admin area.
In my case, i used w3tc, and disabled it with a un-tick.
In other cases, you might also want to disable heartbeat with this plugin https://wordpress.org/plugins/heartbeat-control/
I didn't notice too much of a difference since i'm on a vps. But if you're in shared hosting, this will help.
Then i found out that, you just need to disable object caching on your caching plugin and they will speed up your admin area.
In my case, i used w3tc, and disabled it with a un-tick.
In other cases, you might also want to disable heartbeat with this plugin https://wordpress.org/plugins/heartbeat-control/
I didn't notice too much of a difference since i'm on a vps. But if you're in shared hosting, this will help.