Congratulations on your first cut. It looks much nicer than my first for sure, and I’m positive you learned a lot.
I agree with Frank above. Quartz is ideal for learning the craft, and decent rough is certainly cheap enough. I recommend cutting several round brilliants to hone your skills.
As far as selling it goes, if he wants to buy it go ahead and sell it to him. I suggest you don’t attempt a re-cut though. You might find that you’re just going down a rabbit hole and lose the beauty of the cut as it is.