Hello Associazione,
Did you add the image on the content? Or added the featured image? In a single post, featured image will appear at the top and if you add other image on the content, other image will appear there. We think you added the image in the container so that such images are appear there. So, instead of inserting the image on the content, please add on the featured image.
If you have any problem, never hesitate to ask.
Regards,
Acme Supports