Created a h4 but font not responsive on code block

Hi there. 

I'm working on a bilingual text on a website.
For this I created an English text style (h3) and a Spanish one (h4) with the same specifications as h3,
except for a color change, and insert it on the page with a code block.

h4 has been set to match the size of h3  on full width but for obvious reasons it won't resize 
on smaller screen sizes. Any idea how to solve this? 

Here's a link to the page. 

Thanks!