Wow! Action-packed! Left me hanging on every word. Good stuff :)

Feedback:
"The bullet got him on the arm.": elborate more on what you did for thr bullet to get there
"What do you want? And how in the hell did you escape the Seal? Answer me!" I gripped the gun so tightly, my knuckles turned white. (Change held into gripped and turning into turned) 
He pinned me on the wall. I thrashed my arms and kicked from his hold, but the demon just tightened his grip on my neck.⬇(Improved: He forcefully pinned me against the wall, causing me to thrash my arms and kick in an attempt to break free, but the relentless demon only tightened its grip around my neck.)
"choked it on his ashen soul.": i have no clue what that saying means

His essence tastes like death and smoke. It almost choked my lungs, but I sucked on his soul even still. Hard and eager. Once again, I am enticed. I am lust. I am fear. I am darkness. I am--. my eyes snapped open and felt my irises turn white. 
(Could be improved)

"Show yourself demon!" I reloaded the gun. Movement caught the corner of my eye.


Could have been said better: 

"Reveal your presence, demon!" I confidently reloaded my gun, my attention suddenly caught by a swift movement in the corner of my eye.

"With force, I shut my senses down, grabbed my gun, and aimed at his head. My hands could not stop shaking.I missed. Fuck."

I think you could elaborate more especially the shooting part. There was another sentence that also didn't have it

Hi there, you’re welcome. I believe prologue is important for establishing your book's background and setting the tone. You could put relevant words and maybe elaborate its importance in the story a bit more (without dumping too much information) just so the reader won't be lost. 

Thank you for the clarification. I wish you the best in your writing journey.