Your position on naturalism

[Whateverist]

Thank you for what I take to be a genuinely held position on your part.  We've been suffering a barrage of Poes and trolls so not something to be taken for granted.  I'd love to explore this with you if you're game.  

If everything is natural, then we deny principle of sufficient reason,

I probably need you to unpack that for me.  Whether or not things have a sufficient reason, I would never assume we are equipped to understand them all.  So something which seemingly lacked a sufficient reason might well have one like that, which we just can't comprehend.

..because every natural being being defined by its nature which in turn must be defined by what is not defined by nature, the beyond natural, the super-natural or supernatural.

Why should that be?  Aren't you begging the question of whether any such thing as the supernatural exists, smuggling it in without arguing for it?

But, I think no one can deny sufficient reason coherently, because everything we observe, we know that it must have a sufficient reason. Therefore, not everything is natural and hence there exist at least one supernatural being.

This seems to just repeat your last paragraph.