for translate we use translate API or from google or from Bing.
"el" for Greek
It go from API for definition Greek language.
For replace "el" to "el-GR" - will need rewrite as self component and also htaccess rules
You may try in htaccess set so rules
RewriteRule ^(el-GR)/(.*)$ components/com_seftranslate/translate.php?seflang=el&sefurl=$2 [L,QSA]
RewriteRule ^(el-GR)$ components/com_seftranslate/translate.php?seflang=el [L,QSA]
But need check and debug will that work or also need rebuild seftranslate modul and component
Also I would like to ask how can I add these languages, britihsh english, austria german, belgian french, usa english, ausralian english etc
Bing and google translate APi not support usa english,britihsh english - there is only english
Also right now www.escortsday.com/el/ gives 404. I have put the rewrites at .htaccess.
Have I forgot anything?
Please reread on your site sefTranslate help page, if that not help, please give to us admin and FTP access to your site and we will check where error.
Your account details you may send with help OrdaSoft support form