change only the theme language

My wordpress admin is in french.
and my theme is in arabic.
i have two files mo : arabic and french.

i used this :

add_filter( 'locale', 'change_locale' );
function change_locale(){ return 'pt_AR'; }
load_default_textdomain();
load_textdomain('responsive', get_template_directory().'/languages/pt_AR.mo');

i have my site web in araic only if i deleted the file french pt_FR.mo
if this file exit, my site web is will be in french not in arabic

how can fixed it ?!

Yes, rename your pt_AR.mo to ar.mo and pt_FR to fr_FR.mo.

In step one install but not activate yet the plugin Admin in English. Edit the plugin’s php script. Find line with en_US string and replace this string with fr_FR. Save and activate the plugin. Now your Dashboard will be in French.
In step two remove first three lines of your code from theme’s functions.php and replace fourth one withload_theme_textdomain(‘responsive’, get_template_directory().’/languages’);.
In final step go toRéglages -> Général` and select Arabic as your site’s language.
Now you should have your front end in Arabic and back end in French.