Private repos are allowed, although with some restrictions:
Private repositories are only allowed for things required for FLOSS projects, like storing secrets, team-internal discussions or hiding projects from the public until they're ready for usage and/or contribution. They are also allowed for really small & personal stuff like your journal, config files, ideas or notes, but explicitly not as a personal cloud or media storage.
This is reasonable: Codeberg is specifically set up to be a code host for open-source projects, not for closed-source commercial code.