firewyvern fluid

were can i get firewyvern fluid im guessing from kut ku but i have nevergot one

As the item name suggests, wyverns that spew fire, such as the rathalos, rathian can be carved for them. The item also turns up randomly as rewards.
A side note that your cat explorer can also find some for you, it is again random here except that it can be obained in such a method without confronting the rathalos/rathian.

Monster that may give you the item as rewards are:

Kutku/(blue)
Garuga
Rathalos
Rathian

I forgot about the rest. LOL

You can only get it from the four monsters oz listed. Garuga is the best monster to fight for them, since most the time you get at least one in rewards.

do the easy 2* rathian quest with devil slicer.
I am quite sure you get it there.
(Make sure to break her as much as possible)