Can I use both sprints and Kanban in the same project?

Yes, you can freely mix sprints and Kanban in the same project. You can have projects that only use sprints, or only use Kanban boards, and projects that use both sprints and Kanban boards.

You can freely decide which backlog items should be worked on in sprints, and which should be worked on in Kanban boards. You can also move backlog items between sprints and Kanban boards if you change your mind.