I noticed that for some reason, I can't click the first two offers. I inspected the element, and now I can see this (first attachment).

How to remove it?

Do you use jquery 1.x?

Yes. You can see that the frame is even in the preview of the theme.

You must change ID on button in main.php:
                <button type="submit" id="home-search"><?php _e('Search', 'sofia'); ?></button>

ie into:
                <button type="submit" id="home-search-button"><?php _e('Search', 'sofia'); ?></button>

You then have to go to style.css and global.js and update "home-search" related to button into "home-search-button"