unpublish the form

Hey @Leoni! Welcome to our Community! 
You cannot "unpublish" a form, however, there is a feature that gives you the option to close your typeform to new responses.
To do that, you'll need to open your typeform from your Workspace, and click on the Settings icon. Then you'll click on "Access and scheduling".

A new menu will pop up, and then you just need to toggle on the option "Close typeform to new responses". 

Your respondents won't be able to fill it out anymore. If this is not exactly what you want, your other option is to delete your form. You'd have to go to your workspace, click on the three dots beside your form and select "Delete.

Let me know if any of these ways would work for you! I hope they do! Wishing you a great day!