To get the menu and all the fields in Arabic language following are the steps:
1) Export Po file
First go to Administration -> Translations -> Import / Export -> Export a Translation File

Than select the module which you want to translate in arabic

After selecting the module click on Get File to export the po file.
Now make changes in the po files, write the equivalent arabic translation of english for all the menus and fields.
Example:-
#. module: base
#: model:ir.model,name:base.model_res_partner
#: field:res.company,partner_id:0
#: field:res.partner.address,partner_id:0
#: field:res.partner.bank,partner_id:0
#: field:res.partner.event,partner_id:0
#: selection:res.partner.title,domain:0
msgid "Partner"
msgstr "شريك"
After making the changes in the po files import that po file as
Administration -> Translations -> Import / Export -> Import a Translation File

Now click on Preferences


Select the language which you imported.
Now after reloading you can see the translated menus and fields in Arabic

You can see that the values of all the fields are also translated

