Illdy - Responsive Design doesn´t work on Android and iPhone 5

the headline is not displayed correctly (responsive design). Words are getting cut off and moved to the next line. I have solved the problem with additional Css like it is explained in your support forum. However, headlines are only displayed correctly using the iPhone 6. With the iPhone 5 as well as with Android, it doesn’t work out. What can I do to get headlines shown correctly on all devices?
The Website is:

Thanks for your help!

Hey there

I hope you are well today and thank you for your question.

You can try achieving this by adding the following CSS code in the Custom CSS option of your theme on the below path.

Admin Area -> Appearance -> Customize -> Additional CSS

/*for small devices*/
@media only screen and (min-device-width : 320px) and (max-device-width : 568px) { 
#about > div.section-header > div > div > div > div > h2 > strong > font > font {
  font-size: 30px;

Best Regards,

Unfortunately, this doesn’t work. The headline is still the same. For iPhone and Android.