Deleting an album or gallery would mean losing all the photos and date with it permanently.

Choose the album inside a project that you wish to delete. On the left hand side, find multiple settings amongst which click on Album Settings.

The option Delete Album will prompt you about how you will not be able to undo this step, and therefore helps you delete that album permanently.

Deleting a gallery works in a similar fashion. On clicking the project you want to delete, on the left hand side, find Gallery Settings in the multiple configurations available.

The option Delete Gallery will inform you that this step cannot be undone and thus help you delete that entire project completely. That data can never be retrieved again.