Please teach me more about Swedish folklore and the Tomtar?

Hey my dear alter Schwede!! I’m gonna be this week in Stockholm for work. It will be my first time visiting Sweden. I’m fascinated about folklore, cultures and anthropology, and specifically interested legends and (fantastic?) beings. I’d love to learn more about Tomtar in your culture, that is, about their real impact in everyday life and traditions. Maybe share some childhood memories ? Stories your grandmas would tell you?

Will be staying in downtown Stockholm, but won’t have much free time, please let me know if there are any specific places around that I can visit to learn and experience more about this?