[SOLVED] Image size in Gallery modal view

I tried already a lot, but I didn't get the right responsive result, may be you have a hint:
I want to have the images in the gallery in the modal view without a margin (vertical without margin at top and bottom, horizontal without margin at the sides), the image must be smaller due to responsivness.
In the picture enclosed you see an example, the picture has big margins, the white color is the area the image should fill out.
What is the override css?

There is no margin applied to the images. I'm guessing that's coming from your Joomla template. The only padding applied is a minor amount to prevent the image from sitting directly on the edge of the modal window, but it's maybe 1/10th of the margin you have. Switch to default Joomla protostar template, clear Joomla cache, then see if that large margin is still there. Aside from that it could be white space in the image it self and nothing to do with CSS. Recommend right clicking and inspecting element on the image to review its CSS in your browsers developer console to see what's going on exactly.

Thanks, I did the change to the protostar and cleared all the cache, but the situation is the same. The white space I added to show how big I want it. But it is small with a big margin.

I tested it with a video, a video fits without big margin into the modal area, that is good. So this works with my template, so why not with images (they are big enough and could fill the area).

I've no idea. I assume the image is either too small to fill the space or you've some external CSS conflicting and causing it to be smaller than it should be. Images can fill as much space as you're seeing with the video and large ones do in my tests. Only way to find out is to use your browsers developer tools and inspect the image to see what's going on.

oh no! I realized, that in the gallery plugin settings the max size can be added, that's it!!!! Sorry for this post and thank you!