poor quality images on mobile

We are finishing the design of a website,
We have problems with the display of the images on the mobile, they look of very poor quality, only in the mobile view

in configuration
We had activated: LAZY LOAD, we stopped this and it seemed like it worked better, but we see that it didn't,
If we put the phone vertically they come out poor quality, if we put it horizontally they come out good

we fear in 48% in adapted images

If we touch these parameters, do we have to manually delete them on the web or are they created again?

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