Friend wants to give me power of attorney- i don’t want it

For context my friend Alex and I are in our mid 20s. We were friends in university then did not speak for 3 years following and only re-kindled our friendship one year ago. I have only seen him in real life once since and have never met his family or long-term partner. His life has been complicated and he has few friends.

He has asked me via Wattsapp if I will "sign [his] power of attorney paperwork" I said I would do some research because I didn't understand that term, he said that was ok then later asked if I'm "ok with witnessing the attorney thing".

I now understand that power of attorney means making large financial and health decisions on a person's behalf and I don't feel I'm an appropriate choice for that. Even if I am witnessing the signature of someone else, most likely his partner, it still would not feel right as I have never actually met any of the major people in his life.

Please can you advise a polite way of wording that I am not comfortable signing these documents?