A: Have you heard what happened to Steve?
B: About the car accident? [Here it would be more natural to remove 'about', and say 'The car accident?' or 'That he got into a car accident?'. We would answer with the word 'about' if the question used the word 'about', for example 'Did you hear about what happened to Steve?'] Sure [Here we would say 'yeah'. 'Sure' is only used for 'yes' when we are agreeing to a suggestion. For example, 'Do you wanna come with me to the cafe? - Sure!'), I’m still shaken [This is okay, but 'shaken (up)' implies that you were in the accident or you were there when it happened. 'Shocked' might be better here]. That’s awful!
A: Did he fall asleep while driving? [This is perfect, and we also have an idiomatic phrase, 'fall asleep at the wheel' which we use more often] He’s a bit out there ['Out there' usually describes ideas or actions, not people. For example, 'that idea's pretty out there' means that idea is pretty crazy. 'Crazy' or 'wild' would be a better adjective here.] but he’s normally very cautious as [better: 'when'] he drives…
B: Really? I actually never liked Steve’s driving, it’s kinda sketchy. ['Sketchy' is okay, but usually refers to a person/place/thing that you feel has ulterior negative motives, like a sketchy neighbourhood or a sketchy deal. I'm having trouble thinking of an adjective equivalent. I would probably either say 'Steve's a bad driver' or describe more specifically why it is bad, like 'it's really jerky' (stopping and starting abruptly)]
A: I never noticed! Poor fella… Well, I guess it’s just how it goes sometimes.
B: Yeah… And you know what’s crazy? I was supposed to join him that day but I took a rain check
A: No way! Why didn’t you go?
B: I got swamped at work by the end of the day [More natural would be: I was swamped with work by the end of the day] and couldn’t make it
A: I’ve got goosebumps all over my body, you could’ve died too!
B: I know, right?