Mobile font size for mobile doesn’t work

I have just published my first blog and customized it. The font looks great on desktop but anything lower (table and phone) the body font is way too small.

I already changed it from 12px to 14, 15, even 16px but there doesn’t appear to be any change.

How do we fix this? Most of my audience is on mobile and I’m not super familiar with Ava’s Afro different viewports.

ideally we should be able to set the h1-h6 sizes for each vof the three viewports.

The page I need help with: [log in to see the link]