JSFiddle - React, Tailwind, and code Playground

HTML

<div class="testimonial-outer"> <span class="prev"><</span>
 <span class="next">></span>

    <div class="wrapper testimonial-container">
        <div class="testimonial-wrapper">
            <div class="section-title">
                 <h3><?php echo the_sub_field('section_title',$postID);?></h3>

            </div>
            <div class="testimonial">
                <div class="testimonial-left">
                    <img src="<?php the_sub_field('testimonial_image',$postID);?>" alt="">
                </div>
                <div class="testimonial-right">
                    <div class="testimonial-right-inner">
                        <?php the_sub_field( 'testimonial_copy',$postID);?> <span><?php the_sub_field('testimonial_by',$postID);?></span>

                    </div>
                </div>
            </div>
        </div>
        <div class="testimonial-wrapper">
            <div class="section-title">
                 <h3><?php echo the_sub_field('section_title',$postID);?></h3>

            </div>
            <div class="testimonial">
                <div class="testimonial-left">
                    <img src="<?php the_sub_field('testimonial_image',$postID);?>" alt="">
                </div>
                <div class="testimonial-right">
                    <div class="testimonial-right-inner">
                        <?php the_sub_field( 'testimonial_copy',$postID);?> <span><?php the_sub_field('testimonial_by',$postID);?></span>

                    </div>
                </div>
            </div>
        </div>
        <div class="testimonial-wrapper">
            <div class="section-title">
                 <h3><?php echo the_sub_field('section_title',$postID);?></h3>

            </div>
            <div class="testimonial">
                <div class="testimonial-left">
                    <img src="<?php the_sub_field('testimonial_image',$postID);?>" alt="">
                </div>
                <div class="testimonial-right">
             ...

CSS

.testimonial-outer {
    float: left;
    width: 100%;
    background: #fbb52e;
    padding: 40px 0 74px;
}
.testimonial-outer .section-title h3 {
    color: #fff;
}
.wrapper {
    width: 996px;
    margin: 0 auto;
}
.testimonial-outer .testimonial {
    float: left;
    width: 100%;
    padding: 37px 0 0;
}
.testimonial-left {
    float: left;
    width: 32.3%;
}
.testimonial-left img {
    max-width: 100%;
}
.testimonial-right {
    float: right;
    width: 65%;
    padding: 50px 0 0 70px;
    background: url(images/quote-start.png) no-repeat left top;
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
    margin: 43px 0 0;
}
.testimonial-right-inner {
    float: right;
    width: 100%;
    background: url(images/quote-end.png) no-repeat right 90%;
    padding: 0 70px 0 0;
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}
.testimonial-right p {
    margin: 0 0 11px 0;
    color: #555555;
    font-family: Calibri;
    font-size: 15px;
    line-height: 20px;
}
.testimonial-right span {
    float: right;
    color: #555555;
    font-family: Calibri;
    font-size: 20px;
    line-height: 24px;
    font-weight: bold;
}
.clear {
    clear: both;
}
.testimonial-container {
    margin-left: 0px;
}
.testimonial-wrapper {
    float: left;
    width: 996px;
}
.extra-wrapper {
    margin: 0 auto;
}
.testimonial-outer {
    position: relative;
}
.next {
    color: white;
    z-index: 999;
    position: absolute;
    right: 2%;
    top: 34%;
    font-size: 78px;
    cursor: pointer;
    background: rgba(30, 30, 30, .5);
    width: 50px;
    height: 50px;
    display: inline-block;
    line-height: 45px;
    padding: 15px;
    text-align: center;
    border-radius: 100%;
    border: 3px solid #c48100;
    -webkit-transition: all .25s ease-in-out;
    -moz-transition: all .25s ease-in-out;
    -ms-transition: all .25s ease-in-out;
    -o-transition: all .25s ease-in-out;
   ...

JavaScript

var theTestimonial = jQuery('.testimonial-wrapper');
var theWidth = theTestimonial.width();
var widthCount = theWidth;

jQuery('.testimonial-container').wrap('<div class="extra-wrapper"></div>');
jQuery('.testimonial-container').css('margin-left', '0px');

jQuery('.extra-wrapper').css({
    width: function () {
        return theWidth;
    },
    position: 'relative',
    overflow: 'hidden'
});

//get total of image sizes and set as width for ul 
var totalWidth = theTestimonial.length * theWidth;
jQuery('.testimonial-container').css({
    width: function () {
        return totalWidth;
    }
});


jQuery('.next').on("click", function () {
    if (widthCount < totalWidth) {
        widthCount = widthCount + theWidth;

        jQuery('.testimonial-container').animate({
            "margin-left": "-=" + theWidth
        }, 750);
    }
    
    console.log("wc:" + widthCount, "tw:" + theWidth, "totw: "+ totalWidth);
});

jQuery('.prev').on("click", function () {
    if (widthCount > theWidth) {
        jQuery('.testimonial-container').animate({
            "margin-left": "+=" + theWidth
        }, 750);
        widthCount = widthCount - theWidth;
    }
    
    console.log("wc:" + widthCount, "tw:" + theWidth, "totw: "+ totalWidth);
});