im new to that whole crypto trading but I have recognized a few times that the buy price is lower than the sell price
I assume you mean the buy price is higher than the sell price, because generally the buy price is lower than the sell price.
Anyway I have seen that on a few trades, but assume it's just a lag. I'm never too concerned and you can't double buy those coins anyway, eventually it catches up. For the volumes that some of these exchanges push through I'm reasonably happy with the service. Mt Gox excluded.