Complex sentence: The stage began in Roubaix and when the peloton went over cobblestones at Querenaing, Ocaña and four teammates together with six others attacked and got five minutes at one point, although the chasing group reduced this to two and a half minutes at the finish.
Split into simpler sentences: The stage began in Roubaix and when the peloton went over a section of cobblestones at Querenaing, Ocaña and four of his teammates together with a group of 6 riders attacked and got an advantage. This advantage was over five minutes at one point but the chasing group reduced this to two and a half minutes at the finish.