How does one implement their duties according to the Bhagavad Gita?

I’m a bit confused with how one figures out whether one is a brahman, a ksatriya, a vaisya or a sudra in this day and age. Could someone please explain this?

I’m a bit confused with how one figures out whether one is a brahman, a ksatriya, a vaisya or a sudra in this day and age. Could someone please explain this?