Pathfinder: wildshape; beast shape

[Scottlang]

How does this actually work??
Do you take on the entire stat block of set creature ie a wolf and hp, and when reduced to 0hp you turn back at your hp before wild shape in 5e?? Please help, in the current game I'm running I want to use a Firbolg with 6 level of druid, and I was thinking of starting in the form of a cave lion, there is also going to be 2 x rock trolls and a Buggane in combat... And I can't see how the spell works to get the best effect.

[stack]

Don't read too much into the abilities beyond the text and forget everything about 3.5 and 5e polymorph stuff. Beastshape tells you what you get (natural attacks, some abilities off the list if the creature has them, movement modes capped at the lower of the cresture and the spells limit, size (limited to a certain range).
When you cast this spell, you can assume the form of any Small or Medium creature of the animal type. If the form you assume has any of the following abilities, you gain the listed ability: climb 30 feet, fly 30 feet (average maneuverability), swim 30 feet, darkvision 60 feet, low-light vision, and scent.

Small animal: If the form you take is that of a Small animal, you gain a +2 size bonus to your Dexterity and a +1 natural armor bonus.

Medium animal: If the form you take is that of a Medium animal, you gain a +2 size bonus to your Strength and a +2 natural armor bonus.
You keep your base stats (plus the listed bonus), hitpoints, etc.

The general polymorph rules cover gear merging, continuous items still functioning, etc. If I wasn't on my phone I would go into more detail.