My site is full of Duplicate links like

www.guru99.com/system-testing.html
www.guru99.com/system-testing/12-tutorial/advertising.html
www.guru99.com/system-testing/12-tutorial/index.php
www.guru99.com/system-testing/12-tutoria...aretesting/index.php

Will enabling Joom SEF solve this problem?

NOTE: I have an acitve Joom SEF subcription but the component is disabled in my site due to some issues. If the component can solve the above problem , I will hire a developer who can solve all problems

Hello,
I'm sorry, but I can't tell for sure, it depends on why there are such duplicate URLs created. We would need to find the places where those URLs are created and with SEF completely disabled check their original non-SEF structure, to see why they're duplicated.
You can either do this by yourself and post some examples of non-SEF URLs for the duplicated SEF URLs, or you can purchase our paid support service and we can check this for you: www.artio.net/e-shop/support-services/joomla-related-support-1h

How do i get the non-SEF URLs ?

You need to completely disable SEF on your website in Joomla's Global Configuration to see the non-SEF URLs.