Image optimization: WEBp and png

Hello all,

I am working on one website where I get one different type of challenge for image optimization.
When I check any URL in google page speed then I got one suggestion that is "Serve images that are appropriately sized to save cellular data and improve load time" for image optimization.

For image optimization, I need to change the formate from png to webp so is it the right option?

When I check the image URL in a separate tab and download then I got only webp file formate for download as below SS, Why does it happen
?

there is any SEO point?

I tried to use webp formate but safari does not support and when I click on image to save then why it's showing webp formate?

But when I test in google page speed it's showing the png version.

strange!!!