Hi Toufiq,
I'm not sure if this only happens when I open images from a gallery which is shown in a MODULE Gallery. See Link, images are too big, not resized and visible for mobile devices:
http://www.responsinator.com/?url=https%3A%2F%2Fporta-aviarta.ch%2Fbilder%2Fst%25C3%25A9phanie-berger-mit-no-stress%2C-no-fun-26-mai-2018.html
thanks again for checking.