Website not fully Responsive

Hi - I’ve just launched my site and the Jumbotron on the homepage is not fully responsive on smartphones but ok on ipad.
See image. How can I rectify this :

Hello there,

I hope you are doing well today.

I tested the page but it adjusted correctly. Could you tell me what screen size / device you tested it on? Also, an image would be helpful too.

Best Regards,

Hi its on I-phone 6 and 7 so far. Other pages are not quite adjusting with the Jumbotron titles either. Typically it’s putting the ‘S’ in the title on a separate line, so isn’t resizing properly.