How to find error in bootstrap structure?

Question

Bootstrap

Good afternoon dear experts. Can't figure out error in bootstrap structure

<div class="container order">
    <div class="row">
        <div class="col-md-12">
            <div class="row">
                <div class="col-md-8">
                    <div class="tabs-list" id="tabs">
                        <div id="tabs-1">
                            <div class="col-md-6"></div>
                            <div class="col-md-6"></div>
                        </div>
                    </div>
                </div>
            </div>

            <div class="col-md-4 order-total"></div>
        </div>
    </div>
</div>

The problem is that my col-md-8 and col-md-4 blocks stick together. What could be the problem?

Answer 1

<div class="container order">
    <div class="row">
        <div class="col-md-12">
            <div class="row">
                <div class="col-md-8">
                    <div class="tabs-list" id="tabs">
                        <div id="tabs-1">
                            <div class="col-md-6"></div>
                            <div class="col-md-6"></div>
                        </div>
                    </div>
                </div>
                <div class="col-md-4 order-total"></div>
            </div>

            
        </div>
    </div>
</div>