How to open various files(image,video,txt) as pop-up on the current browser page instead of opening in separate page?
What you're describing is a modal window. There's a few modules out there for Drupal that create modal windows. The one that probably best fits your use case (media consumption) is Colorbox. Out of the box, it only handles images but there are a number of supporting modules that can handle other media files. See the Colorbox project page link for more information.