All Namespaces like "Category" "SpecialPages" etc are all in german, but I want them to be in english. How can I achieve that ?
Topic on Project:Support desk/Flow
I know that you can switch the language of your wiki. You can test that with the uselang parameter appended to one of your wiki URLs:
uselang=en
However, this does not only influence the namespace names, but the display of all interface texts. The request to only change the namespace names to a different language while keeping all other interface texts is not very common, I think. Is there a special reason for why you want that?
Yes, I am only on a standard Host that has a pre-set Mediawiki and that is in german, so I can't install it directly in english.
So you actually want the wiki to be in English. This can be done by setting $wgLanguageCode in LocalSettings.php.
The above is the real solution. If you want to be able to use your wiki seriously, you should use a host, who allows you to actually modify your files.
A hack to get the same result might be to add a jQuery script to the wiki page MediaWiki:Common.js, which automatically adds the uselang parameter to all links pointing to your wiki. However, before I would write such a script, I would just go to a host, who gives me access to my files.
The $wgLanguageCode only makes the wiki english, but not the namespaces.
That is partly true: The built-in namespaces are getting translated for me.
Custom namespaces display the name, which is defined in their page in the MediaWiki namespace, e.g. in MediaWiki:Nstab-main for the "Main" namespace. If no translation for that page is present, then - regardless of the selected interface language - the English name will be used. E.g. on page MediaWiki:Nstab-main/de. Otherwise the namespace name will be localized as well.
What you can control in the MediaWiki namespace is the text of the tab, not the namespace itself (eg: when linking to pages in that namespace or the displayed URL). See Manual:Using custom namespaces
If links to these namespaces should be updated, kind of like a mass replacement, then Extension:ReplaceText will be able to do that.