We try to create a filter for a drop-down selection within a survey. We use the survey as an application form and the participants may select a date. However, we only want a max. of 60 persons at one date, so we would like to set up a rule, were the option cannot be chosen any longer, when already 60 users of the survey selected this option.

Your LimeSurvey version: LimeSurvey Community Edition  Version 5.1.18+211101
 

Please do not ask the same question in different language forums. You have asked this question already in the German forum.
Here the post in the German Forum:
forums.limesurvey.org/index.php/forum/ge...-anzahl-an-auswahlen

Answered in the German part.

Joffm wrote:

Oh, sorry

What are YOU sorry about, Joffm?

Thank you @holch. 
Since I'm new to the forum, I did not know this rule.
 

Since I'm new to the forum, I did not know this rule.

Well, then you must be new to the "internetz" as well. Cross Postings are generally not very liked, in any type of forum.