Adapt custom section in Cactus Pro theme

Hello,

I’m using the Cactus Pro from VelaThemes and would need your help please. I’d like to change the look of the Custom section, it should look like the text box in the Promo section. So, this is the content of the template-promo.php:

<script src=”https://gist.github.com/anonymous/e0d1ac0cd6e793ad0e8676ce72af16f9.js”></script&gt;

And this is the template-custom.php:
<script src=”https://gist.github.com/anonymous/2f3343a2d9b26bc8c64a16017d9394e6.js”></script&gt;

What do I have to change in the additional css and in the template-custom.php to get a look like the Promo box (“VITA” on the page http://martinfrank-kabarett.de/website)? The text box should be in the centre.

For now I didn’t change any template, I just added this to my additional css, trying to reach somehow that “box look”:

.cactus-custom {
width: 50%;
margin-left: 334px;
background-image: url(“http://martinfrank-kabarett.de/website/wp-content/uploads/2018/02/bg.png&#8221;);
background-repeat: no-repeat;
background-position: bottom;
padding: 58px 0;
box-shadow: 1px 1px 4px 3px rgba(0,0,0,.1);
}

On my desktop it looks good so far (but maybe not on yours, ha?!), it’s a total mess and not adjusted in the mobile version at all. 🙁
Screenshot: https://img1.picload.org/image/daalapiw/mob-version.jpg

I hope you can help me, thank you so much in advance!

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