Site Title Not Responsive

Hi!

There is a problem when I visit my site from a mobile device, it appears a blank space on the right of each page. It looks like the title is too wide and doesn’t fit on mobile size. I have tried to enter different css commands but it doesn’t work.
Could you please advice?
The page I need help is: https://std18.me1click.gr/

The page I need help with: [log in to see the link]