Site Title in Bold

@dajobbindia If you’re looking to apply CSS styling to your sites header in reader mode you can add the following to your themes functions.php file, or preferably a custom plugin.

add_action( 'amp_post_template_css', function() {
        ?>
.amp-wp-header a {
    font-weight: bold;
}
        <?php
} );

For further CSS changes please refer to online resources, we can only assist with plugin related issues.

It seems you’re using the GeneratePress theme, you could use the themes AMP add on and then switch to transitional or even standard mode AMP, with a working navigation menu and AMP URLs that look the same as your current site.

Thank you for the solution and for the suggestion as well.