3 if you're good at the game

if im not verry good?

It realy depends on the lynel, because it can have 2000 health or 5000(these have a stronger hit).But if you are fighting a 5000 health one and you are average I think 12 hearts will be enough.

I am not sure if they had 4 digit healt or a 5 digit

You can beat a Lynel in 5 seconds with a guardian arrow