Our problem is, that our Confluence is very slow and we found the reason. When an editor places an image and scales it, then the browser still load every time the big file and not the resized image. E.g. 2,5 MB just for one image.

Confluence should resize it to the size (e.g. 300px) and use it for the preview. When you click on it, then it should load the original image or also optimized to the disply e.g. 1200px.