Site title cut off on mobiles

My site title is cut off on the right sight, shows only about 20 of 25 characters, on my own mobile and using Inspect in the browser: all mobile phones!
I use Agama free version and Header V2 in Customizer.
Agama claims to be a responsive theme. So this seems very odd to me. I switched to Agama recently and consider to switch to another theme.

Also because a large part of the header image is cut off on the left and right side on mobiles, instead of shrinking to fit. Image has recommended size 1920×960 px. I use(d) Viewport Height 65 instead of the default 50, in case that matters. With default setting for viewport height the result for the header image is somewhat better for mobiles, but on lap-/desktop a large part of top and bottom of the header image are not shown. I’m going to try to fix this using another crop of the original photo and may have to add a coloured border around it to get it right for most screen sizes.

The header image is something I think I can fix myself, although I regret Agama makes it hard to get this right. (Or am I missing something?)
But the site title I think the theme should take care of. How best to fix the site title so it is shown correctly for all common screen sizes?

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