Optimizing your images is one of the quickest ways to boost your site’s speed...

https://spencersgreatjournal.wpsuo.com/why-does-google-pagespeed-complain-about-properly-sizing-images

Optimizing your images is one of the quickest ways to boost your site’s speed and search visibility. Start by renaming files with descriptive keywords instead of generic numbers, then add helpful alt text for accessibility