Kingdom of Knuffel

You're over 580 years old but you only look 24.

You are 200

You fool people a lot. You have a calm wisdom that makes you seem very aged, but actually you haven't even reached 30 yet!

You're something like 300

18 soon to be 19

You look so ready to Party that you must have the energy of youth.

I'll call you 17.

I would give you around 12

That's the most polite way anyone has ever called me immature. :P
Nah, s'all good.

Okay, let's see, I'm going to say you are... 42! The answer to Life, The Universe, And Everything (as per Douglas Adams)

XD

I think you're more or less 300 and YES that's young

Hmmmm, lessee. You still look like a dryad to me. They live a long time, depending on their tree types, but ornamental cherries aren't the longest-lived of trees, just a few hundred years, so maybe you're around 80 or 90?