Hi.
Which is correct:"to not prevent something from happening" , or, "not to prevent~"?
'Not to prevent' is almost certainly better. In future, please give more context; it is sometimes difficult to tell from just three words.
Context is always important; labelling is rarely important.
Please read my words. I wrote, "'Not to prevent' is almost certainly better." (emphasis added)
Context is always important; labelling is rarely important.
If one is better than the other, then it should be clear that they are both possible.