Max image with 1280px

Hi,
I use full width images sometimes. As soon as I activate WebP Express, the plugin will use the image with 1280px width instead of 1920px. How can I change that?
Check the full width image in the first section. It’s loaded at 1280px width and does not look really good.
https://www.dein-fotograf.de/eventfotografie/

The page I need help with: [log in to see the link]