Reduce number of resized images

Hi,

I want to drastically reduce the number of automatically resized images.
Now one image has almost 10 clones (see attachment 1). This is absurd, as I am building a webshop with over 3000 images, and so the number of files is insane.

I would just like 1 original image, an resized version of 800px and maybe a thumb for the overview page with products. No other automatic resized extra duplicates of an image needed.

1/ Which settings do I have to adjust ?
2/ Which plugins do I have to use to accomplish this, and maybe to remove old resizings ?
3/ It is weird, I have under customizer > Woocommerce > product image > main image width : 1200px. But on a product detail page, it still displays the original uploaded image, which is sometimes 1800X1600. How can I make on the product page, that the version of 1200px wide is shown ?
4/ When looking at the source code of an image in the “shop page” with all the thumbs, it uses a variety of sizes for other screen sizes. Can this also be altered, so I only end up with 3 image sizes : original – 800px – thumb.

Thanks