Can you clarify why the angels Harut and Marut taught people witchcraft and then tell people not to do it? And are these angels still living? If so, where?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The reason why the two Angels Haaroot and Maaroot taught people magic was that Allaah Almighty wanted to test His slaves. That is why they never taught anyone except they would tell him that it was a trial and would warn him against disbelief, as Allaah Almighty Says (what means): {But they [i.e. the two angels] do not teach anyone unless they say: “We are a trial, so do not disbelieve [by practicing magic].}[Quran 2:102] that is, "don't learn magic in order to harm anybody, which leads you to disbelief." With Allaah is ultimate Wisdom and the far-reaching [i.e. conclusive] argument over His slaves.

We are not aware of any narration by the Prophet telling us whether these two angels are still alive or dead, or where they are if they are alive. Asking about such matters is of no benefit for the Muslim. See Fatwa 82269

Allaah Knows best.