I have a Plex media Server and in my Plex account another server from a friend.
The Problem is that his Server seems to be the Standard server. I always need to click the burger menü and click on one of my libaries. When i click on the configuration icon i get the settings for my server so i dont know how to change this behavior
Which client type are you using?
The behaviour you describe is usually rectified by resetting the home page of the client and to go through the ‘first-run wizard’ again.
Here it is described for the web app:
https://support.plex.tv/articles/customizing-plex-web#toc-4
Android mobile
https://support.plex.tv/articles/customizing-the-mobile-apps-2/
other client types https://support.plex.tv/articles/categories/player-apps-platforms/
