Sharing on facebook as post

I have a problem with sharing the posts from the website. When I share the post on facebook, the image that is shown in the post is of my logo and not the one that I have attached on the post. How can I change this?

I have tried with other social networks and everything is fine, only facebook makes trouble.

Thank you in advance for the help.

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