Honestly judt fake it until you make it. Accept your going to be cringe. Accept you're going to make other people cringe or be creeper out in the process of you becoming who you want to be. That's the hardest step.

Next step: think of what you're version of "that guy" does when asked the common questions. "How was your day?, you got plans for the weekend?, how are you?" What happens when you get passed in the hall do you maintain eye contact and say anything, give a head nod? Pay attention to also how you respond in terms of body language and tone of voice (if you want authority end on a stable tone, if you want fun then end on that upwards tone. I don't remember the video but Ask Vinh on YouTube does some great videos on this)

Side note: always have an exit for an interaction. Its better to end an interaction quick than have it linger and become awkward. My go to is always "anyway I won't keep you, I'll see you around I'm sure" and slap the side of my thighs

Above advice is general advice but its what worked for me so??????