Dear Sir,
I have read your problem for the website to be slow. There are many reasons those make your site slow for browsing e.g. Code is not optimized correctly, SQL queries are not written in efficient way, big queries written for small tasks, Cache is not clearing on time and many more. When you'll supply us the details of your website than our developer will analyze the site and find out what's there making your site slow. Once he find the reason he'll quickly solve those issues. How much time it will take, it depends on the size of the website and number of issues found. At the end, we'll give you a super speed site.
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Hope to hear from you soon.
Best Regards
Zeeshan A.