caremyway-client/src/components/Topics.jsx

import React from "react";
import { Route, Link } from "react-router-dom";
import { Container } from "semantic-ui-react";

const Topics = ({ match }) => (
  <Container>
    <h2>Topics</h2>
    <ul>
      <li>
        <Link to={`${match.url}/rendering`}>
          Rendering with React
        </Link>
      </li>
      <li>
        <Link to={`${match.url}/components`}>
          Components
        </Link>
      </li>
      <li>
        <Link to={`${match.url}/props-v-state`}>
          Props v. State
        </Link>
      </li>
    </ul>

    <Route path={`${match.url}/:topicId`} component={Topic} />
    <Route
      exact
      path={match.url}
      render={() => <h3>Please select a topic.</h3>}
    />
  </Container>
);

const Topic = ({ match }) => (
  <div>
    <h3>{match.params.topicId}</h3>
  </div>
);

export default Topics;