How hide border around posts on home page?

Hi,
I am using this great one theme on my website https://kamzici.ctujm.cz/ and i want to ask for css edit I think…How can I hide border around posts on home page? Here are screens, I mean it would be better than 100 words…

• actual look of page
• what i want hide

I want hide only black line. I want green line for separation of posts.

I am using plugin Posts in Page on my home page. Plugin is using shortcode [ic_add_posts template=’loop-blog.php’] for action.

I hope you know how hide it.
Thank’s, ShippeR