Featured image showing up strange in posts

Hi everyone! I wonder can anyone help me…I have to set featured images for my posts for a post carousel but when I do it some of these featured images appear really big and distorted at the top of my post pages, like in this post: http://www.arelaxingcup.com/ci…. I tried looking up ways to hide them online but they all talk about changing code in files I can´t find in my Editor. Thank you so much for your help-I really appreciate it!