Featured Image Size On Mobile and Tablet

Hi, I need to know how to resize the featured image sizes on mobile for Catch Fullscreen. The desktop version of the website is perfect. However on mobile, I cannot see the full image and it is being cut off (in portrait mode, landscape on mobile is also perfect). Is there a CSS code I could add to fix this? Or is there a way to disable the mobile version of the website entirely? Website: www.efendihookah.com Thanks