What protected actually means
Protected means somebody else is on duty and you are genuinely off. Not resting on the sofa within earshot. Off.
It means the monitor is with them and not with you. It means your phone is in a different room, because the part of you that scans will use a phone to scan with. It means you have agreed in advance what they will and will not wake you for, so you are not lying there deciding.
Four hours unbroken is a good target and three is still worth having. It does not have to be every night. Two or three nights a week changes how the other nights feel.
One thing this course will not do is tell you how to feed or settle your baby. Those are decisions for you and for your midwife or health visitor, and how you arrange cover around them is yours to work out. The principle is only this: one stretch, one other adult, agreed beforehand.