Featured photos different size and cannot adjust them

I have been reviewing books by posting it on my wordpress website. Anyhow, after I upodated the theme, I found that the featured image size was cropped. It is like wordpress resizes the photos automatically. You can see cropped photos in the red square compared to the full size photos below.

I would like to demonstrate the photos in full size so I resized it on wordpress, try to find higher pixel and upload it. Redo it over and over again, but still doesn’t work.

Anyone can help me with this issue? It would be really high appreaciate.

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