So I want change the URI of the Homepage 1-home but the Panel doesn’t offer me this button. Also I may need to translate that URI too. Thank you in advance 
localhost/home/site ~> localhost/ownName/site
I tried to search the forum and docs but couldn’t find anything …
You can do that via content options: https://getkirby.com/docs/cheatsheet/options/home
To translate the URI, you can use the URL-Key field: https://getkirby.com/docs/languages/urls
never mind … I figured it out - thank you for the hint
Old message:
I tried c::set('home','home2'); but it’s not having an effect …
Have you actually renamed the folder to home2, then?
Just to make sure there is no misunderstanding: Why do you want to translate the URI of the homepage? After all the homepage URI is not visible to users as the URL they will be seeing is just http://example.com/ without the folder name of the homepage.
in my specific case the homepage had subpages and if you visit a subpage it looked really weird 
In my test it worked, I renamed the home folder to “start” and set my config accordingly:
c::set('home', 'start');
Now the “test” subpage is available at: http://www.example.com/start/test
While setting the home option works for the default language, I don’t think you can translate the URL. It may look like it’s working, but there are a few edge cases (e.g. duplicate content prevention by redirecting /home to /) where it probably won’t work.
In which file do I change the content options? Thanks!
In “site/config/config.php”