Advertising Banner Wrapper

Hi

I am using the Classified theme, version 6.5 with version 3.9 of WordPress.

I use an eBay banner on my website using the Advertising part of the theme. Unfortunately, the banner is not responsive, so when viewed on smaller screens or mobile phones, the banner is much wider than the body of the site.

Unfortunately, eBay do not do an option of a responsive banner, therefore I am restricted to making the wrapper on the website responsive.

I have been able to do this manually, in Google Chrome by pressing F12 and adjusting the width to 100%. However, I have not been able to find a way to do this with the CSS code as the wrapper seems to have a code that changes each time the page is loaded.

For example, #epn-ads-banner107228135 or #epn-ads-ctr107228135.

Does anybody have any idea on what I can do?

My website is https://thelarptrader.co.uk

Thanks

Darren