Add this as custom css

.listing_wrapper.col-md-4.property_unit_v3.property_flex.propety_unit_3 {
width: calc(50% – 16px);
}

Change the thumb size images as in this help https://help.wprentals.org/article/how-to-change-the-image-size-for-listings-card-units/ 

You may wish to modify some design elements and that may require using a custom css.

You can add custom css in Theme Options > Design > Custom CSS. The modifications you do here are NOT overwritten when you do a theme update.

To see css changes, you will need to clear cache.

• The theme offers a basic child theme in the theme pack. This allows you to make changes to your site without modifying the parent theme – so you can add custom css in style.css file from the child theme.  When a new version of the parent theme is released, after you update it on your site, all your modifications from the child theme are saved and it won’t be affected or lost.
  Help article for child theme install

If you cannot see your CSS applying, it means you add the wrong CSS code or you have cache. An alternative that overrides any cache and lets you preview the changes is WordPress – Customizer (WordPress default functionality)