Reduce space between widget blocks

Is there somebody who can help me to reduce the space between widget blocks in the sidebar. I tried it already with css in the customizer. It works with the classic editor but not with the blockeditor:

.widget-area .widget h3 {
	color: #003a6b;
	font-family: Open Sans;
	font-size: 12px;
	line-height: 1em;
}

The page I need help with: [log in to see the link]