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’);.Réglages -> Général` and select Arabic as your site’s language.
In final step go to
Now you should have your front end in Arabic and back end in French.