How can I create a new Namespace? But I also like that my new Namespace will appear in "Search for contributions/Namespace:" and when I search, in the "Advanced Search Options" box.
How can I create a new Namespace? But I also like that my new Namespace will appear in "Search for contributions/Namespace:" and when I search, in the "Advanced Search Options" box.
Also see Help:Custom namespaces.
Means that I can only make my own namespace when I ask on Special:Contact/general?
OK, and when I like to test first my new namespace?
You can't - they will add it and you start using it. You could create your own test wiki and get it created there, but there really isn't anything to "test" with a new namespace.
Read the requirements at Help:Custom namespaces. If it meets the requirements, yes (unless Staff find it fit to decline your request for some other reason).
I saw that on Lego Wiki there are more then 3 new/own namespaces. It says on Help:Custom namespaces that more then 3 new namespaces are not allowed. But how did they got more then 3 new/own namespaces??