Image getting pixelated on site?

Hi,

On my site https://takanodan.net, the image is very pixelated when it gets smaller. How can I remove this? Do I need to pull it up in Gimp or something in order to soften it?

Thanks

What are you viewing the site on when it gets smaller? I checked it on my phone and my desktop…the images aren’t pixelated at all

The header image appears pixelated.

What browser are you using? Are you looking at it on a mobile device? What resolutions? What monitor size?

Using firefox on a Mac pro and a 30 inch monitor it looks fine. On a samsung galaxy 9 it looks fine.