Hello @Thomas_Roos,
Just to confirm, you’re referring to a dashboard you created from scratch from your Reporting tab?
By default, these dashboard are private to their owner. They can be shared with other Organisation members but can’t be made public all in one click (like you would for a project or task). If you haven’t yet, I’d recommend upvoting this other thread from our Product Feedback category: Ability to share Reports Org Wide - Set public reports as default