the “/#/vsc.php” before the question mark is necessary. So I tried the following inside quform:
I made a confirmation type “Redirect to custom url” and entered the URL “/wohnen-preise/unverbindliche-anfrage/#/vsc.php”. In the query string field i entered the following: calendar_date_from={element|id:5|Anreise}&calendar_date_to={element|id:6|Abreise}
I added a screenshot below.
When I now fill out the form and submit it, the redirection looks like this: /wohnen-preise/urlaubsbuchung-zauchensee/?calendar_date_from=2020-10-30&calendar_date_to=2020-11-07#/vsc.php