Inline Popup change size

Hello,
i tried to setup a popup window and want to change the size.

I installed php code:

function inline_popup_enabler(){
?>
<script>
(function($){
$(window).load(function() {
$(‘.inline_popup’).magnificPopup({
type:’inline’,
midClick: true
});
});
})(jQuery);
</script>
<?php
}
add_action(‘wp_footer’, ‘inline_popup_enabler’);

After this I created a Popup window with ID demopop and CSS mfp-ide.

if I click an a link on my testpage the popup opens. But the width is on the full screen.
I tried to change the custom CSS like this:

.page-id-demopop .mfp-iframe-holder .mfp-content {
line-height: 0;
width: 100%;
max-width: 1600px;
}

.page-id-demopop .mfp-iframe-scaler {
padding-top: 56.25%;
}

But it don’t work!!! (!Important) didn’t help

Any solution?

Thanks!