Difficulty in Customising image

Hi all,

For the top image in http://sreejishlals.com/book-detail.html 1, I am unable to provide a 830×260 image as it will be very stretched then. When I tried a 300 x 398 px image, perhaps as the class slide width above the image is set at 722 px, the image shown is very large.

I am unable to find div class=“slide” encompassing this image in the html and css files.

I purchased this Book Store Responsive Ecommerce HTML5 Theme from Envato Market recently. Unfortunately, as this author is removed, I cannot get support from them.

Please provide your valuable suggestions on how to find this file and how to fix this issue.