Page getting glitchy on mobile

Hiya!

I'm really happy with my site, but right at the bottom, my page seems to overflow on mobile? I've attached a photo but I can't work out how to fix

Here is the solution:

.item-pagination[data-collection-type^="portfolio"] {
	display: flex;
	justify-content: space-evenly;
}

#itemPagination a.item-pagination-link{
	padding: 4px 18px 4px 18px !important;
}

Apply this code only in media query with max-width: 428px

Sorry, where do I put this? 

Inside Website Tools > custom css

@media only screen and (max-width: 428px) { /* for mobile */

	.item-pagination[data-collection-type^="portfolio"] {
		display: flex;
		justify-content: space-evenly;
	}

	#itemPagination a.item-pagination-link{
		padding: 4px 18px 4px 18px !important;
	}

}