This is completely unrelated to our software. We do not modify your files or your site's output. We take an exact copy of your files and your database contents. On restoration, these files are written to disk and the database contents are simply restored to the database. The only thing the restoration script does -besides connecting to the database and restoring the database contents- is to modify the configuration.php file of Joomla! to tell it "use that database" where "that database" is the one you specified on restoration.
Akeeba Backup cannot and will not replace, edit, modify or otherwise modify your site's template or language settings. These are the only things that control the HTML output of your site. In fact, the language tags are entirely controlled by the language plugin of Joomla! and your template. I'm sorry, but we cannot provide generic support for using Joomla! itself. All I can do is point you to
Joomla's multilingual site documentation and kindly ask you to review this information, especially steps 2, 3 and 7 which seem to be applicable in your case.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!