@Olga Lilke -

assuming you have the right permissions (e.g. Team Admin, owner of the projects), you can delete the projects by going to the Miro dashboard, click on the team logo in the left vertical teams bar, then click on the project in the Projects list, then click on the project name itself. Once that is done, you’ll get a dialog box with a Delete project option in the lower right (see below).

If you wish to delete a team, click on the team logo in the left vertical teams bar, then click on the teams name below the “Miro” label in the top left of the dashboard. This will bring you to a new screen which will enable you to delete the team (see below).