How do I get the layot a bit more compact - Default Theme /OJS3


I try to get the layout of the Default Theme a bit more compact.

Please look at:

The white gap above/below the brain (Vol 1 (2020)) and below the section headers is quite big.
I tried it with a custom css file including:

.section {
padding-top: 5px;
padding-bottom: 5px;

but without success.
Has anyone an idea?