How to remove polygon

[rachelflynn]

Hi! Thank you so much for creating this theme, I love it!

I am not a programmer, but I have been trying to get started by creating my own website. I am using the theme for my online portfolio, so each of the "posts" contain a different document that I have created. I took a screenshot of each document to use as the post image, but I do not want them to appear in the background of the post since they are primarily text.

I have tried for four hours to remove the polygon from the background of each post, but I have been unsuccessful. I have tried removing different portions of the CSS code, but it completely removes each post from the page. I was hoping you could possibly point me in the right direction to remove this.

I have attached a screenshot of this issue, but here is a link to my page.

Thanks so much!