Font styling won't apply with code

I've added the below code, however on this page, it seems to be stick on 500 weight font?

h1 strong,
h2 strong,
h3 strong,
h4 strong,
.list-section-title strong {
    font-family: @heading !important;
    font-weight: 400 !important;
}

// LESS BOLD, BOLD FONTS ➷ ☯ ☯ ☯ ☯ //
strong {
    font-weight: 400 !important;
}

Can you share your website URL?

Out of interest, why are you setting the text to bold and trying to unbold it is CSS?