Hello kourkos,
Notice that’s the normal theme behavior when a background image has been added to your theme. The layout will be boxed. Provide your website URL so I can take a closer look at it and also, so I will be able to provide a more accurate response.
Thanks for your understanding!
This happens only in beauty theme. For example to other themes happens this 
my site is wikiherb.gr
Hello,
I have inspected your website and it seems that the demo works well, as you can see here -> https://www.screencast.com/t/aU4knUrgB5 Where’s the problem? Clear all the caches, browser caches and check the results.
Thanks for the message!
Hello kourkos,
Try the code below ->
.td-blog-beauty .td-category-header {
margin-bottom:0;
}
The code is -> https://www.screencast.com/t/7LuzsZC8zVYc
Thanks.
