我的导航栏隐藏了下面的内容。而且，它粘在左边而不是中间部分。我希望有人能告诉我正确的方法来使导航栏正确的方法来使粘性导航栏停留在它的位置，即使我们正在滚动。
代码sanbox https://codesandbox.io/s/clever-voice-24udr
Navbar.js

import React, { Fragment } from "react";
import { Link } from "react-router-dom";
import { Button } from "react-bootstrap";

const NavbarPage = () => {
  const guestLinks = (
    <ul>
      <li>
        <Link to="/">
          <Button className="btn btn-primary createNew">Create New</Button>
        </Link>
      </li>
      <li>
        <Link to="/about">
          <Button className="btn btn-danger signOut">Sign out</Button>
        </Link>
      </li>
    </ul>
  );
  return (
    <nav className="navbar bg-white">
      <h3 className="titleName">
        <Link to="/">
          <i className="fas fa-pen" /> demo
        </Link>
      </h3>
      {guestLinks}
    </nav>
  );
};

export default NavbarPage;

.navbar {
  position: fixed;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.7rem 2rem;
  overflow: hidden;
  z-index: 1;
  width: 88.15%;
  margin: auto;
  top: 0;
  border-bottom: solid 1px var(--primary-color);
  opacity: 0.9;
  top: 0;
  box-shadow: 12px 0 15px -4px rgba(31, 73, 125, 0.8),
    -12px 0 8px -4px rgba(31, 73, 125, 0.8);
  box-shadow: 0 9px 0px 0px white, 0 -9px 0px 0px white,
    12px 0 15px -4px rgba(31, 73, 125, 0.8),
    -12px 0 15px -4px rgba(31, 73, 125, 0.8);
}