Hi there @alessandro_romolo_e !
You can limit the access of the project to just yourself. Jira admins by default still will see the project in the project list, but will not be able to see the issues inside of it. They can add themselves to your project access (that is what the Jira admin role allows), and you could check if they have done so by navigating to the Jira system settings and going to the Audit log.
From experience, the best way to keep it truly private if you're working with other same/higher-level admins, is to use something like Trello or another app where the same admin permissions don't apply.
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