它在桌面上运行良好，但在响应模式下出现问题

<header class="header">
        <nav class="navbar fixed-top navbar-expand-sm bg-warning">
            <div class="container">
                <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav"
                    aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
                    <span class="navbar-toggler-icon"></span>
                </button>
                <div class="collapse navbar-collapse" id="navbarNav">
                    <ul class="navbar-nav">
                        <li class="nav-item">
                            <a class="nav-link active" aria-current="page" href="#">Home</a>
                        </li>
                        <li class="nav-item">
                            <a class="nav-link active" href="#about">About</a>
                        </li>
                    </ul>
                </div>
                <a class="navbar-brand" href="#">My Project</a>
            </div>
        </nav>
    </header>

我花了两天时间还没弄明白。