Only display Avatar in Admin panel

I run a multisite WP. I want users of subsites to be able to post on forums managed by your Forums plugin, from the front office, and manage only their avatar , managed by your Avatar plugin, in the backoffice.
This means removing almost everything in the backoffice except the Avatar menu.
I tried the Ultimate Branding but it does not enable me to remove options in the menu displayed on the left side.
Please tell me if it is possible and how to proceed.