Input Field for zipcode won′t show up

This is caused by your theme:
https://piratenpartei-mv.de/wp-content/themes/scapegoat-master/style.css has

/* Honeypots */
ol.cf-ol #li--7, ol.cf-ol #li-2-6, ol.cf-ol #li-3-6, ol.cf-ol #li-4-6, ol.cf-ol #li-5-6, ol.cf-ol #li-6-6, ol.cf-ol #li-7-6 {
	display: none;
	padding: 0 !important;
	margin: 0 !important;
	border: 0 !important;
}

The Honeypots do not appear in https://github.com/zutrinken/Scapegoat/blame/master/style.css so I guess it is a customization by you or someone who managed the site before you.