Thank you for getting back to me. Yes I did. I copied and pasted the project and tried to open the backup file but when I do it opens the Composer and shows me the experiences panel. When I then select the project it tells me that the experience was created in version 6 and can't be opened in 5. I also tried renaming the backup file to ifx.backup_5.7.6 but it still opens only the Composer.
The reason why I need a rollback is that my clients still have the version 5 Players. To upgrade the Players they need administration rights from their IT department. The IT department can't update the Players until next month. I want to create the rollback so that they can still use the experience for the time being.