on of my friends website he but areas in city can you please guide me how to add areas in city

You mean to add city area to search?

yes also people can select that area to post the ad as same county province then city then i want to add area option where i can i add all cities areas as one of osclass user added

Currently there is not functional architecture for this in osclass.
In theory, if you would manually loaded city areas into database, you would be able to create autocomplete etc, but any kind of management is missing in backoffice.

Maybe it could be added once in future, but for me it looks bit like overkill 

please check this website i m talking about it
timesinpakistan.com

I have no idea what should I check.

sorry by mistake link error its that one
https://www.timeinpakistan.com/
they have use areas in city

screen shot its city then its area

You have city right now there so your design does not somehow align.
Create city & city + city area as quick solution

i do not understand i just ask you how to add areas after city

There is no answer on "how to...".
Develop it.