Post-navigation NEXT on same row as PREVIOUS

Hi, you helped me some years ago with a little CSS code that don´t seem to be working correctly anymore. They next and previous post navigation links are still aligned on the same row, as I like them, but the arrow to the far right is now just a "little box". I guess somethings is wrong with the font icon code. And there is an extra arrow (probably the original arrow) on the left side of that next nav linktext, that I want to hide.

I want it to be one arrow to the far left with linktext, a gap, and then the link text with one arrow to the far right.

This is my old CSS:

/*Next blog-post on same row*/
.post-navigation {
    display: flex;
}
.post-navigation .nav-next {
    width: 50%;
    text-align: right;
}
.post-navigation .nav-previous {
    width: 50%;
	color: #ed8a63;
}
.post-navigation .nav-next .next:before {
    display: none;
}
.post-navigation .nav-next .next:after {
    font-family: GeneratePress;
    text-decoration: inherit;
    position: relative;
    margin-left: .6em;
    width: 13px;
    text-align: center;
    display: inline-block;
    content: "\f105";
    -moz-osx-font-smoothing: grayscale;
    -webkit-font-smoothing: antialiased;
    font-style: inherit;
    font-variant: inherit;
    text-rendering: auto;
    line-height: 1;
    speak: none;
	color: #ed8a63;
}

I just changed from Floats to Flexbox, but I do not think that is the problem. I belive it been like this for a while, I have probably just not seen it.

By the way, I could not see any change in the site layout or in loading time/size after changing to Flex. Maybe a caching thing? Or site already okey? But can you see/confirm that my site now uses Flex? Would it be best to delete the GP theme and install it totally fresh again to remove old stuff?! (This is a simple site with not to many configurations...)