For example, this works at the current width of my browser:

@media screen and (max-width: 1300px) and (min-width: 1201px) {
   .mvp-feat3-text h2.mvp-stand-title {
    font-size: 47px;
   }
}

You’ll need to play with your browser width and adjust the font size appropriately when each breakpoint kicks in.

To add CSS:

• If you are using WordPress 4.7, use the “Additional CSS” option in the customizer.
• If your theme has a custom CSS option, use that to add the CSS shown above.
• If not, install the plugin Simple Custom CSS.

Learn to use the Chrome Developer Tools to help you see and test changes to your CSS.

I hope one day I can recognize things like that myself! Total beginner in that field =D

Best wishes,
Anke