This is the 3426th most frequent Swedish word.
bestämma
"Bestämma" means "to decide" or "to determine" in English.
Here, 'bestämma' is used reflexively with 'mig' to indicate the act of making a personal decision.
Jag måste bestämma mig för vilken bok jag ska läsa.
I need to decide which book I am going to read.
In this case, 'bestämma' is used in its standard form to refer to collectively agreeing on a decision.
Vi ska bestämma datum för mötet imorgon.
We will decide the date for the meeting tomorrow.
Here, 'bestämma' is used with the preposition 'över' to denote authority or control in the context of making decisions.