React link does not refresh the page

I am using react-router-dom version 5.2.0, and when I clicked on Link, the page will not refresh, I have to do it manually.

App.js: `import React from "react"; import {

BrowserRouter as Router,
  Switch,
  Route,

} from "react-router-dom";

import './App.css';

import NavigationBar from "./components/NavigationBar";

import Hero from "./components/NavigationBar/Hero/Hero";



function App() {
  return (
 <Switch>
   <Route path="/contact">
     <h1>ahoy</h1>
   </Route>
   <Route path="/">
   <div className="App">
      <Hero />
    </div>
   </Route>
 </Switch>
</Router>


);
}

export default App;
`

NavigationBar.js: `import React from "react";

import "./NavigationBar.css"

import { Link } from "react-router-dom";

const NavigationBar = () => {
    

  return (
      <header className="NavigationBar">
         <nav>
           <ul>
             <Link to="/"><li>Domů</li></Link>
             <Link to="/contact"><li>Kontakt</li></Link>
             
           </ul>
         </nav>
       </header>
    )
  }
export default NavigationBar;`