I have tried to edit the site title under customize in other language than English and when I load the page the site title still shows as English.
Changing default locale has no effect whatsoever, the title and the description stays the same no matter what language I select.
Those are site settings right? They are locale independent AFAIK, so you will need to manually edit and fill in the content in the language of your preference.
Not sure why you got the expectation of automatic translation, can you expand a little bit on that?
Sorry I don’t understand what is your objective here.
Do you want a different title for each locale?
yes, exactly that what I want @Falco
Different title and description for each locale, because I want to enable set locale from accept language header.
Oh I see. I don’t think we support that at the moment.
None of our site settings are keyed on the locale, only the UI strings support that (the ones you can change under the customize admin screen).
This is a reasonable feature request, but it may be a tricky one to get right.
I change js.login.header_title activate set locale from accept language header and it will load the correct header_title according to the locale, but not changing the title and the description?
There is no way to overwrite the UI version using the locale from the server and client language specific files? I want the title and the description to be other language not English when the forum is used by Spanish people. 
You can fill those site settings in Spanish, and they will show Spanish and Spanish only.
The problem is that enabling set locale from accept language header will show everything in Spanish except the title and the description of the site.
If another user from Turkey loading the site, that user will see everything in Turkish but not the title and the description which is always remains English which is a big problem.
Also all topics and posts will be written in their original language.
While Discourse can be used for multi-lingual communities, either by giving each language a dedicated category or by relying heavily in the Discourse Translator plugin, Discourse is not, and at the moment doesn’t aim to be, a software that can handle a 100% localized experience using a single instance.
That gives you two options:
Work with an okay but not 100% experience in a single instance.
Have a different Discourse instance for each locale your company/service servers.
We have customers using both solutions, but each has it’s ups and downs. There are many discussions on the subject on the Topics tagged multi-lingual tag.
The site language is a setting that tells Discourse to use different texts for each locale. These texts are included in your Discourse installation. Anything that a user/admin has manually put in does not change based on a language setting AFAIK.
A dumb thing I made ages ago was a PHP script that used a GeoIP service to find a user’s country, then automatically translate parts of the site text into the country’s native language using the Google Translate API.
Do you change your name when you speak a different language? Why would a web site?
But I think that you could make a theme component that would do that with some ease. If any of thousands of people using Discourse had needed that (and also thought it was armature) absurd) not to change the title when locale changed there would be a mature theme component already in available. But now you’ve found your place to contribute. Depending on how many things you want to customize for each locale, I’d guess it’s $250 to $1000 of work (which you can do yourself if you have the skills and desire).
Actually, with schema.org possible to describe multiple or the same things: Language - Schema.org Type
Add a property CreativeWork with the URL of http://example.org/c/espanol, with a custom title, description, inLanguage inLanguage - Schema.org Property.
Add them:
https://example.org/admin/customize/themes/1/common/head_tag/edit
Search engines will understand it, that different categories are in different languages to which you can give any title, description etc using schema.org. Each CreativeWork is a category representing a language.
You can add many CreativeWorks into the header as you like.
This way don’t need to mess with modifying discourse at all, while allowing you to signal it to search engines that your main site is called XYZ in different languages.