Thank you Jonah for you help
Very kind of you
Now I figured out how I have to do it.
I duplicate all custom html and all other modules, change the language and of course assign it to the specific language menu. So that works.
But I'm not sure if I did it right with the "homepage". I duplicated the menus also the home. In the tutorials I watched there was mentioned that I need the Main Menu then language specific menus. And the default page has to be from the main menu "home". The Main menu has to exist like a hidden menu and then the visitor get redirected to the language specific website.
As I copied everything should be the same but on my website now I have some kind of category blog at the home site? When I click on one masonry icon it's displayed below the pictures there and does not display the blog like on your Demo site? Also the Picture Blog does not work. Kind of strange.www.florianhirschhuber.eu
Would be the site.