Blurry image after page loading

Hi everyone,

I’m developing with a theme using the classic WordPress Editor. On this page, you can see the image that contains circles on the bottom right hand corner. When the page loads, I can see it clear for a few miliseconds and then it becomes blurry. On some screen sizes (wide ones especially), the image is displayed properly.

Because of this, I thought it might have been because of the natural WP images resizing, so I went to “Settings” => “Media” and turned every value to 0. It doesn’t change anything. I also downloaded a plugin designed to disable lazy loading: doesn’t work either.

The original size of my picture is way bigger than what it looks like on the screen, so it’s not a resolution or a size problem.

I need to tell you that my problem is not due to a Retina screen, I’m on a PC using Chrome. I tried it on Firefox and Edge too, same problem.

I can’t think about another solution. Please help me !

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