Serving Translations Without Changing The Url

how to make cs cart Serving translations without changing the URL like magento ?

Use your URL?sl=[lang_code]. When it sees this, it will change the language and invoke the url without the 'sl' parameter.

{$config.current_url|fn_link_attach:“sl=$language.lang_code”|fn_url}" with Language code ok .

how to make this url parameter without lang code “{$config.current_url|fn_url}” ?

You can't change the language without submitting the sl url parameter. You could POST it rather than GET it to hide it but it still needs to show up in the REQUEST.