Im having the Problem That all contents i insert are getting these half transparent backgrounds ( No its Not in the Column or cell backround Settings ) and there are no Settings for That or i cant find it - do someone know where to remove it?
Looking at your screenshot I note that the background image is also bleeding over your bookmarks toolbar thus outside the Elementor window. And the fact your Elementor control panel is also transparent this looks to be local computer orientated.
A simple test would be to disable all plugins > select a one of the standard themes ie Twenty Sixteen see if you still have the problem
you can switch to the basic WordPress theme without actually affecting anything just for the purpose of testing this but I do not think because the pattern is visible through the elemental control pattern panel that you need to look at your machine.