Problem with Simple Masonry gallery plugin (mobile devices)

Hello,

I know this might not fit in this support forum, but i’m hoping someone can help.

This is my website:
http://www.francisconoa.com

For each post i’m using a gallery with this plug in:
https://wordpress.org/plugins/simple-masonry-gallery/

the problem is that, while on the PC the display has no problems, on mobile devices the width never adapts to the screen display.
I have tried making these change to the code, but no matter what changes i insert they do not affect the plugin (but if i alter other things like site width etc all is fine…)
These are the changes i did:

@media screen and ( max-width: 1200px ) {
	.site {
		width: 600px;
	}
	.single .content-area,
	.page .content-area,
	.search-no-results .content-area,
	.error404 .content-area {
		width: 100%;
	}
	.simplemasonry-item .masonry-brick .simplemasonry-container {
		Width: 400px;
	}
	.single .hentry,
	.error404 .hentry,
	.page .hentry,
	.search-no-results .no-results {
		width: 500px;
	}
	.site-info {
		line-height: 1.6;
	}
}

Please let me know if anyone can help or indicate me if the problem is with the plugin and not with the Theme.

Many thanks in advance!
Cheers!