As long as you are the only participant in the meeting, the meeting will automatically delete itself as soon as you leave it (tap on "More" in the upper right corner). In general, if everyone leaves, the meeting will be deleted.

Otherwise, only we from the Meet5 team can delete the meeting for you. A short mail to support@meet5.de is all it takes. It's best to let the other participants know in the group chat so that no one wonders why the meeting can no longer be found in the app.