Thank you for writing in, I see that you're wrapping your text in a headline tag. This is also the reason why your responsive text selector seems to not affect the headlines.
<h1><span style="color: #cde13e; font-weight: bold;">Campen Group</span></h1>
<h3>Training & Coaching Solutions</h3>
Please use the headline element instead if you need it to be a headline. Those headline tags have font-size associated to it (h1 = 400%, h3 = 228.5%) those amplify the test font.
Regarding the Root Font Size, it seems to be set to 14px on all screens? Please set a smaller value for font size (XS) and font size (SM).
Hope it helps,