Help how long could it take?

[singularity3]

How long could it take to lose consciousness from complete hanging with a slip knot?

 

[Foreverix]

It depends. If the ligature cuts off enough blood flow in your arteries, it could be as quick as 10-15 seconds. If it just made you choke, it might take a minute or two. There's no real way to know for sure until one commits to it.

For what it's worth, a few videos I've seen of folks filming their complete hanging depicted a pretty swift drift into unconsciousness. There was no struggle, no thrashing, just their head would go purple and expand a bit and then they'd go limp. Maybe those were extraordinary cases, I don't know.