It is impossible to tell how long it takes any site to be reviewed. Some sites are reviewed in minutes, others take days, weeks, months, or even longer. It depends on when a volunteer editor has time to review the site.
The Web Design categories are notoriously backlogged, and your specific category is no exception. I recommend waiting
at least 3 months before checking on the status of your site.
Your site may qualify for an additional, independent listing in the Regional/ branch. Given your contact information, you should also submit your site in
http://dmoz.org/Regional/Asia/Pakistan/Provinces/Islamabad_Capital_Territory/Business_and_Economy/Internet (where -- luckily for you -- there is much less of a backlog). Suggesting your site in this category will not affect the chances (or speed of review) of your original suggestion in any way; the decisions regarding eligibility in these two categories are completely independent.