When should i use đừng instead of không
Không has a stronger meaning than Đừng. Đừng has a bit of begging in it while Không has the sense of prohibition.
To elaborate off NgocBichLe10, 'đừng' is used to ask someone else not to do something. As for 'không', it is used for commands.
Examples (excuse my poor Vietnamese):
"Đừng khốc con ơi"
"Don't cry oh little one"
Lol love this sentence
I don't know, asking someone (a child presumably, or a partner that's into that kind of thing) to not bite you seems like a scenario where you would be using không. Unless you don't mind being bitten!