How do I start listening to what people say and responding in the moment? Without a pre-thought-out response.

I'm trying to talk to people more, but it does not feel like talking, all my responses feel like I'm following a rough script, I try to focus on what they are saying but my automatic reply to everything seems to just be to nod and smile, then I think of what I should have said 5 minutes later when I'm no longer talking to them.