Responsive layout issue

Hello,

I am using the Highend WP Theme and encountering issues with the responsive design for small screens (such as iphones). I am using the Side Navigation Heading option which uses h1 text settings for the site title. However, when I open my website on an iphone held vertically, the site title does not minimize to fit the screen and thus runs into/through my mobile navigation button, rendering it useless. Not sure how to fix this.

Thank you!