Chapter 1: Hello, I saw your request for a co author, aswell as I am a beginner writer. This is my opinions so please do not be offended in any way. I see your style is to talk like this:
Chanyeol: Y/N, I didn’t expect to see you here.
I would like to show you a style I prefer, though nothing against your style.
Just then, the familiar-faced man opened his mouth to speak.
“Well hello Y/N,” he tilted his head and smirked, sending shivers up your spine, “I didn’t expect to see you here.”
Suddenly, a spark flew in yoru brian as memory was pulled up and out from long ago. Blood rushed to your face as you remember that horrible, painful day.
“You... Chanyeol,” you managed to sputter out, “Why are you here.”

This text is just an example, but see how I can portray more emotion easily through the speaking? Though your style may be different, you may want to try to add some descriptive emotions between speech. Also I apologize for any mistakes.