ibadrehman

Any issue in settings can cause this behavior. You may perform a few check ups to ensure that plugin and WP is configured properly for commenting.

From your WP settings, click on discussion and enable “Allow people to post comments on new articles” if not enabled already.
Ensure that your posts are configured to receive comments. (From WordPress live editor).

Follow complete directions from here: https://www.wpsuperstars.net/disqus-missing-comments-troubleshooting-guide/

If the search field is originated from a Widget then you can easily remove that widget from your page. If the search is hard coded then instead of modifying its HTML or PHP, try making changes in its CSS. For this you may use any debugging tool and give the CSS property to display: none; . You just have to find out its origin.