i found an easy solution for this problem... and it works like a charm.
i use 2 laptops... on one i need arabic keyboard and the other i need russian.
no modules nor key bindings helped... so the best way was to use addlocale
you have to add the locale u need... lets say farsi here... and when u come to the step of chosing the keyboard layout(the most important step which u may lose in the middle) u chose the farsi one...
then in the next step it will as you to chose a button for toggeling the keyboard layout... i usually chose the "left windows button"
then when i finish and restart i just relaunch the addlocale app and chose english( to revert to english interface... i just want the keyboard not to have the whole interface translated ... this depends on your preference ) and restart...
after that u will have an english interface... but if u need to toggle between the english& farsi keyboards u just use the "left windows" button.
it works great with me... and all the keyboard is functioning with no problems at all on both languages
hope this was enough and easy explanation.... have fun