React BrowserRouter routes with a parameter are not loading the CSS files, why always not importing CSS files in react js routers, I'm trying to setup a react-router for my first React webapp, it seems to be working except that the css doesn't load

import { Route,Switch } from "react-router-dom";
import Allmeetup from "./pages/Allmeetup";
import Newmeetup from "./pages/Newmeetup";
import Favourite from "./pages/Favourite";
import Mainnavigation from "./Layout/Mainnavigation";

function App() {
  return (
    <div>
    <Mainnavigation/>
<Switch>

  <Route path='/' exact>
    <Allmeetup/>
  </Route>
  <Route path='/Newmeetup'>
    <Newmeetup/>
  </Route>
  <Route path='/Favourite'>
    <Favourite/>
  </Route>



</Switch>
</div>
   
  );
}

export default App;

import { Link } from "react-router-dom";
import {classes} from './Mainnavigation.module.css';

function Mainnavigation()
{
   
  return (
      <div className={classes.header}>
          <nav>
              <ul>
                  <li>
     <Link to='/'> Allmeetup</Link>
     </li>
     <li>
     <Link to='/Newmeetup'> Newmeetup</Link>
     </li>
     <li>
       <Link to='/Favourite'> Favouritepage</Link>
       </li>
       </ul>
       </nav>
</div>

  );

}export default Mainnavigation;