Hi @designerajb, thanks for the good question. First, the form on the site is directly coming from Mailchimp, so it will be difficult to control how responsive that is on small screens without using some custom CSS code.
What I would recommend instead, is to create the form in Webflow, then use the Mailchimp instructions found in the university to configure your form to post new form submissions at Mailchimp: MailChimp form Integration | Webflow University
This way, you can design the form responsively as you wish in Webflow and have that be responsive on all screens and still submit to Webflow.