Hello @MulderDSM,
Thanks for asking. 
- Please make sure to clear browser and server cache. After that try turning of breadcrumbs and footer menu.
- Please make sure you are using the most recent version of X 6.1.6 and Cornerstone 3.1.6.
- Try increasing your PHP Memory limit. You can do this by editing your wp-config.php file which can be located under the root of your WordPress installation.
Add the following lines into that file.
define( 'WP_MEMORY_LIMIT', '512M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
4. You also have the option to hide Breadcurmbs and Footer menu using custom CSS. You can add following CSS under X > Theme Options > CSS:
.x-breadcrumb-wrap {
display: none;
}
.x-colophon.bottom .x-nav {
display: none;
}
If you would like to learn CSS, I am sharing few resources that you take a look to get started with CSS and an interesting tool that you can use to speed up the development process.
I recommend you to watch following video that will help you to get started with CSS.
https://www.youtube.com/watch?v=MFR4WXiLzpc
Sometimes it can get a bit difficult to find out the right selector to be able to write the required CSS codes. A handy tool that can help you in this is Google Chrome dev tools. I am sharing the resource that you can refer to get started with dev tools.
https://developers.google.com/web/tools/chrome-devtools/css/
https://developers.google.com/web/tools/chrome-devtools/
https://www.youtube.com/watch?v=tP_kXBJWPhQ&t=200s
Let us know how it goes.
Thanks.