Optimizing pictures on the homepage (losing speed).

and by the way : i like those one-page websites too – but on page-speed reasons ( and gtmetrix test-results) they have great disadvantages i think. Alot of content to load on starting page. Today a good time to load the first site has to be under 3sec.

a page with over 90% on gtmetrix and over 80% YSlow (the cdn and cookie free domains value is for the most a bad value)
is a good site.
reducing the request on that page is a good advice.
so minifying and combine js and css files is a good thing (use caching tools and minifying tools)

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another point: do all wordpress sites need realy comments or emoji ?
there are two good plugins disable emoji and disable comments

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go and have a deeper look to the waterfall results.

so if you don’t want to make your gtmetrix public – you have to wait til mods are here.

by the way php7 is a resource monster :lol. sometimes – if you can test to switch to 5.6 try.

this is the concerning code in functions.php (parent theme):

$avia_config['imgSize']['widget'] 	= array('width'=>36,  'height'=>36);						// small preview pics eg sidebar news
$avia_config['imgSize']['square'] 	= array('width'=>180, 'height'=>180);		                 // small image for blogs
$avia_config['imgSize']['featured'] 	= array('width'=>1500, 'height'=>430 );						// images for fullsize pages and fullsize slider
$avia_config['imgSize']['featured_large'] 	= array('width'=>1500, 'height'=>630 );						// images for fullsize pages and fullsize slider
$avia_config['imgSize']['extra_large'] 	= array('width'=>1500, 'height'=>1500 , 'crop' => false);	// images for fullscrren slider
$avia_config['imgSize']['portfolio'] 		 = array('width'=>495, 'height'=>400 );						// images for portfolio entries (2,3 column)
$avia_config['imgSize']['portfolio_small'] 	= array('width'=>260, 'height'=>185 );						// images for portfolio 4 columns
$avia_config['imgSize']['gallery'] 		 = array('width'=>845, 'height'=>684 );						// images for portfolio entries (2,3 column)
$avia_config['imgSize']['magazine'] 	= array('width'=>710, 'height'=>375 );						// images for magazines
$avia_config['imgSize']['masonry'] 		 = array('width'=>705, 'height'=>705 , 'crop' => false);		// images for fullscreen masonry
$avia_config['imgSize']['entry_with_sidebar'] 	= array('width'=>845, 'height'=>321);		            	// big images for blog and page entries
$avia_config['imgSize']['entry_without_sidebar']= array('width'=>1210, 'height'=>423 );						// images for fullsize pages and fullsize slider
$avia_config['imgSize'] = apply_filters('avf_modify_thumb_size', $avia_config['imgSize']);

$avia_config['selectableImgSize'] = array(
	'square' => __('Square','avia_framework'),
	'featured'  => __('Featured Thin','avia_framework'),
	'featured_large'  => __('Featured Large','avia_framework'),
	'portfolio' => __('Portfolio','avia_framework'),
	'gallery' 	=> __('Gallery','avia_framework'),
	'entry_with_sidebar' => __('Entry with Sidebar','avia_framework'),
	'entry_without_sidebar'	=> __('Entry without Sidebar','avia_framework'),
	'extra_large' 	=> __('Fullscreen Sections/Sliders','avia_framework'),
	
);

you see that there is allready an image size which could fit for your site (see comment: // images for portfolio 4 columns) – but it is not selectable ( portfolio_small)
so maybe that is enough to make it selectable:

add_filter( 'image_size_names_choose', 'my_custom_sizes' );
function my_custom_sizes( $sizes ) {
    return array_merge( $sizes, array(
        'portfolio_small' => __( 'Portfolio Small' ),
    ) );
}