You bought near the top and that is always a bad idea, Im not trying to bash you or anything but you do not seem to know a lot about trading
That guy didn't do wrong, he bought BTC when it just had dropped (from a short spike, but still) 500eur.
Meanwhile a lot of people started buying, at the top, an already overpriced BCH. And these won. Call it balls or luck, but that goes against your "buy low sell high".
I hope the BCH isn't gonna kill the BTC. It's already going down right now, maybe that will push the BTC back up. Surely it made some people very rich.