Thanks a lot for the quick and helpful answer, Zet Man!

I have a second question. This is my first bigger software project - so I am a bit overwhelmed by the amount of files. Is there a tutorial or something about the file structure?

Exspecially about the location of the function definition files?

And is there a component about geo tracking finished/or in production?

Take a look at my development site https://newblue.ongolito.net
(you may login with demoduck/demoduck)

If this is what you wanted, edit topbar.php of your theme that way that the complete code below becomes part of the if(ossn_isLoggedin()) condition.

Hey
I have the same problem.
I can not find the file which determines the HTML output for the start/register page. The one file which can change the top we behavior I found,(thmes-MyNewTheme-plugins-default-theme-page-line52 echo ossnpluginview("theme/page/elements/topbar");, changes the behavior for all pages (e.g. top bar and navigation disappear after you are logged in.

Which file do I have to change?
And probably how?

Greetings Tobi
=> My theme is a copy of go blue and just changes colours so

Please take a look at https://www.opensource-socialnetwork.org/wiki/view/1063/how-to-develop-a-new-theme take a look the css files and theme files.