index.tsx

import { AppBar, Grid, Hidden, Toolbar } from '@material-ui/core';
// ...

const Header = () => {
  // ...

return (
    <AppBar position="static">
      <Toolbar disableGutters>
        <Hidden mdDown>
          <NavigationButtons />
        </Hidden>
      </Toolbar>
    </AppBar>
  );
};

export default Header;