How to put the menu in front of the cover block so that it can be seen?

Question

css

Good day, dear doctor-coders. I decided to transfer the old landing page to React and the menu on top was no longer displayed for me. I looked through the element code and it is there but behind the cover block. Can you write me pills for this disease? Tried z-index and does not help, probably the case is running.
That's how it was before.

And now there is a logo, but there is no menu.

<nav className="navbar navbar-expand-lg navbar-light fixed-top" id="mainNav">
            <div className="container">
                  <a className="navbar-brand js-scroll-trigger" href="#page-top">
                  <h1 className="text-uppercase">

                  <div className="kingplace-logo">
                    <img src={Logo} alt=""/>
                          </div>
                  </h1>
                  </a>
                  <div className="top_nums">
                    <p className="text-black mb-4"><a href="tel:[phone]"> [phone]</a></p>
                    <p className="text-black mb-4"><a href="tel:[phone]"> [phone]</a></p>
                  </div>
                  <button className="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation">
                  <span className="navbar-toggler-icon"></span>
                  </button>

                  <div className="collapse navbar-collapse" id="navbarResponsive">

                  <ul className="navbar-nav ml-auto">
                  <li className="nav-item">
                  <a className="nav-link js-scroll-trigger" href="#okomp">О комплексе</a>
                  </li>
                  <li className="nav-item">
                  <a className="nav-link js-scroll-trigger" href="#preim">Преимущества</a>
                  </li>
                  <li className="nav-item">
                  <a className="nav-link js-scroll-trigger" href="#price">Цены</a>
                  </li>
                  <li className="nav-item">
                  <a className="nav-link js-scroll-trigger" href="#rassr">Рассрочка</a>
                  </li>
                  <li className="nav-item">
                  <a className="nav-link js-scroll-trigger" href="#plan">Планировки</a>
                  </li>
                  <li className="nav-item">
                  <a className="nav-link js-scroll-trigger" href="#contact">Контакты</a>
                  </li>
                  </ul>


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

And the complete code
https://github.com/fpsstyle228/manchetten