Activation of parallel sprints in a project with same and different team

[Deleted user]

Activation of parallel sprints in a project with the same and different team. For example, we have 2 Teams. Backend and Frontend team. Both teams are working on the same project but different tasks, timelines, and scope. Sprint 1 belongs to frontend team and Sprint 2 belongs to the backend team. At the same time, Sprint 3 also belongs to the backend team. Now I want to active all 3 sprints at the same time but I am unable to do that. Although I have already enabled the multiple sprints checkbox using the administrator site.