Hi
Thanks for contacting us. You can follow this documentation below:
https://www.joomshaper.com/documentation/helix-framework/typography
Tip! To change the font size used for Tablet and Mobile view - please first change the view using top icons Desktop (default), Tablet, or Mobile - then selected font size.
All other options (like Font Weight, Color, Decoration, Line height) are global, so they are used on all views.
https://www.joomshaper.com/images/2021/08/18/font-size-mobile.png
Font size for Mobile view. I hope it will help you. If you need any further help, feel free to ask me.
-Regards.