Call to Action in Home Header

Hi WordPress fans,

I’ve been using the twentyseventeen theme for a while, but there’s a thing I can’t do: I just want to add a simple written on the header main pic. As you can see in the Home of my site, I added a written directly on the header pic with GIMP, but clearly I can’t add a link to the written and it’s not responsive on mobile displays.

I think I have to add the code on Header.php (I’m using a child theme), but can’t get where I have to put the code in the file to have the written centered as I made with my ugly quickfix and what’s the right code to add. Furthermore, I wish to add a link to the written, and put it into a div, so I can customize the CSS and obtain my call to action.

Thank you in advance for your attention!
Andrea Borin

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