I tried Atlassian and decided not to use it. I have a free plan and tried to delete the organization and account. As described in many FAQs there seem to be some apps like rovo, projects, goals blocking the deletion. The FAQ says I should contact support, but there is no possibility for this in free plan mode.
So I hope this way will do it:
Please remove any remaining apps and delete the organization and delete the account.
Thanks, D.