Nothing/ Nothing new/ Nothing much/ Not much. You?
What's going on?
I have insomnia/ I can't sleep./ Oh,nothing. I’m fine./It’s nothing. I’m okay (good,fine)/ Nothing to worry about./ Nothing’s the matter, honestly, I’m fine.
What are you doing?
I'm ------ing
How are you doing?
I'm doing good/pretty good.
What's the matter?
I have allergy. /Oh,nothing. I’m fine./It’s nothing. I’m okay (good,fine)/ Nothing to worry about./ Nothing’s the matter, honestly, I’m fine.
What's new?
Nothing/ Nothing new/ Nothing much/ Not much. You?
What's happening?
I have a cold. /Oh,nothing. I’m fine./It’s nothing.all good.
Hey, man! What's up?
Nothing/ Nothing new/ Nothing much/ Not much. You?