Use my own CSS does not remove css styles from header

I’m trying to clean up the header and when I enable the option to use my own css, it doesn’t change anything. I still see the css styles in the header.

<style>
.scroll-back-to-top-wrapper {
    position: fixed;
	opacity: 0;
	visibility: hidden;
	overflow: hidden;
	text-align: center;
	z-index: 99999999;
    background-color: #008d3c;
	color: #deecdf;
	width: 50px;
	height: 48px;
	line-height: 48px;
	right: 30px;
	bottom: 30px;
	padding-top: 2px;
	border-top-left-radius: 10px;
	border-top-right-radius: 10px;
	border-bottom-right-radius: 10px;
	border-bottom-left-radius: 10px;
	-webkit-transition: all 0.5s ease-in-out;
	-moz-transition: all 0.5s ease-in-out;
	-ms-transition: all 0.5s ease-in-out;
	-o-transition: all 0.5s ease-in-out;
	transition: all 0.5s ease-in-out;
}
.scroll-back-to-top-wrapper:hover {
	background-color: #0b713c;
  color: #ffffff;
}
.scroll-back-to-top-wrapper.show {
    visibility:visible;
    cursor:pointer;
	opacity: 0.7;
}
.scroll-back-to-top-wrapper i.fa {
	line-height: inherit;
}
.scroll-back-to-top-wrapper .fa-lg {
	vertical-align: 0;
}
</style>

How do I remove that and use my own? I do not want any styles in the header, I have this chunk moved to my own stylesheet.

Thanks!

https://wordpress.org/plugins/ajax-load-more/