The prefights are passives, and do not count for buffed up, what you need to do is use Adapt and then do double medium combos to gain furies.
Idk what range your symbiote is, but at rank 2 you unlock the third hability, this said that if you land a medium hit after a medium hit you gain a fury buff. You need to put at least 2 points in this hability and the figth will be easy.