On my homepage, the thumbnails were resized in HTML or CSS, so that they have the same file size as the origonal pictures. But that slows down the website a lot.
Why does WP or GP not serve much smaller scaled images as thumbnails? Is there a way to do that?
yes, I have checked that. But if I set a smaller size, then the mobile view is wrong, because the images stay at that smaller size and react not responsive.
I know from other themes, that they save different sizes from each image, so that they always can serve the right image for each situation/viewport.