I think I found the reason, but I don’t know why.
If I set the Layout of the page to “Fullwidth” then the problem did not appear. But if I set it to “Sidebar Left, Content Right” then the elemets are not in line to each other. And if I change the Site Max Width or the site Width then I can see how the hight is changing…
And ther is enough space for all 4 elements in the width.