I want create word-press menu from scratch

Here is my html Code , I just want to same as it in my word-press menu. I am using .but using this i am only getting parent menu not child. if it's possible with walker menu then please help me. I am using this code for get menu on front-end

'primary', 'container_class' => 'main-navigation' ) ); ?>

<div class="main-navigation">
                                <ul>
                                    <li>
                                        <a href="index.html">Home</a>
                                    <li>
                                        <a class="btn dropdown-toggle" data-toggle="dropdown" href="#">
                                            About Us
                                            <span class="caret"></span>
                                        </a>
                                        <ul class="dropdown-menu">
                                            <li><a href="who-we-are.html">Who are we</a></li>
                                            <li><a href="core-value.html">Our Core Values</a></li>
                                            <li><a href="management-team.html">Management Team</a></li>
                                            <li><a href="customer-partner.html">Clients &amp; Partners</a></li>
                                        </ul>
                                        <ul class="about-us-img"></ul>
                                    </li>
                                    <li>
                                        <a class="btn dropdown-toggle" data-toggle="dropdown" href="#">
                                            Service Offering
                                            <span class="caret"></span>
                                        </a>
                                        <ul class="service-offer dropdown-menu">
                                            <li>
                                                <i class="by-industry"></i><h3>By Industry</h3>
                                                <ul>
                                                    <li><a href="manufacturing .html">Manufacturing</a></li>
                                                    <li><a href="healthcare .html">Healthcare</a></li>
                                                    <li><a href="retail.html">Retail</a></li>
                                                    <li><a href="consumer-durables.html">Consumer Durables</a></li>
                                                    <li><a href="logistics.html">Logistics</a></li>
                                                    <li><a href="ites-bpo-kpo.html">ITES (BPO/KPO)</a></li>
                                                    <li><a href="ecommerce .html">E-Commerce</a></li>
                                                </ul>
                                            </li>
                                            <li><i class="by-function"></i><h3>By Function</h3>
                                            <ul>
                                            <li><a href="sales.html">Sales</a></li>
                                            <li><a href="marketing.html">Marketing</a></li>
                                            <li><a href="supply-chain.html">Supply Chain</a></li>
                                            <li><a href="finance.html">Finance</a></li>
                                            <li><a href="hr.html">HR</a></li>
                                            </ul>

                                            </li>
                                            <li>
                                                <i class="by-tech"></i><h3>By Technology</h3>
                                                <ul>
                                                    <li><a href="qlikview.html">Qlikview</a></li>
                                                    <li><a href="qliksense.html">QlikSense</a></li>
                                                    <li><a href="msbi.html">MSBI</a></li>
                                                    <li><a href="dot-net.html">.Net</a></li>
                                                    <li><a href="sharepoint.html">SharePoint</a></li>
                                                    <li><a href="middleware-api.html">Middleware/API</a></li>
                                                    <li><a href="mobile.html">Mobile</a></li>
                                                </ul>
                                            </li>
                                            <li>
                                                <i class="by-business"></i><h3>By Line of Business</h3>
                                                <ul>
                                                    <li><a href="analytics.html">Analytics</a></li>
                                                    <li><a href="application-development.html">Application Development</a></li>
                                                </ul>
                                            </li>
                                        </ul>
                                    </li>
                                    <li class="drop-resourse">
                                        <a class="btn dropdown-toggle" data-toggle="dropdown" href="#">
                                            Resources
                                            <span class="caret"></span>
                                        </a>

                                        <ul class="resourse-menu">
                                            <li><a href="case-studies.html">Case Studies</a></li>
                                            <li><a href="http://ift.tt/1Q2IYaA">Blog</a></li>
                                            <li><a href="press-release.html">Press Releases</a></li>
                                            <li><a href="methodology.html">Methodology</a></li>
                                        </ul>
                                        <ul class="resourse-img"></ul>
                                    </li>
                                    <li class="drop-career">
                                        <a class="btn dropdown-toggle" data-toggle="dropdown" href="#">
                                            Career
                                            <span class="caret"></span>
                                        </a>
                                        <ul class="career-menu">
                                            <li><a href="job-opening.html">Job Opening</a></li>
                                            <li><a href="life-at-polestar.html">Life@Polestar</a></li>
                                        </ul>
                                        <ul class="career-img"></ul>
                                    </li>
                                    <li class="drop-conatct">
                                        <a href="contact-us.html">
                                            Contact Us
                                        </a>


                                    </li>

                                </ul>
                            </div>-->`enter code here`

If possible then provide me a solution.

via Chebli Mohamed