I'm developing the site in a dev folder and in production mode:
reservacosteravaldiviana.cl/rcv4/
Everything scales just fine once you figure out some of the quirks of Joomla (like if you put an intro or full article picture in the "Images and Links" article option, they won't scale)
Thats odd as I've never had an issue with "Images and Links" images being un-responsive. Do you have any examples where I can see this happening?but on the iPad 1 I get a cut off right edge, both in portrait and landscape.
Not much, mind you, but just enough to be annoying.
I don't have other iPads, so have not been able to confirm the issue on later models, but the fact that there is an issue is enough.
So I checked with my ipad-air2 ios9.2.1 and I see EXACTLY the same as here "The other issue is that on the first site I developed with Gantry 5.1.6:
amsterdampublicidad.com/v4
I was able to put a background image in the header logo/image particle after following the corresponding instructions in the documentation. However, on the new site (Gantry 5.2.

I could not get it to work, in spite of various attemps and repeating the procedure twice.
Still worse, when I updated the amsterdampublicidad.com site to 5.2.8, my home pages (NL, ES, EN) started template crashing, and the only way to get them back up is flushing the cache (gantry and rokbooster plus multithumb are typically there) to get the pages back up for just one click to have them crash again.
Hmm...this really should be straightforward so I'm not sure what your issue is. Would you please start a New Topic for this and post the link back here so I can see it.