Featured image solution not working

Hi to all,
I’m trying to set the featured image size on the post page itself and followed the instructions on pasting code in the customize>custom css/js from amit on this link: https://www.ads-software.com/support/topic/wp-ocean-blog-post-feature-image-too-big/

The image size on the category page changed but on the post itself the image is still huge. Can anyone please help me with resizing to a smaller image size?

The page I need help with: [log in to see the link]