how they manage to stop the car from a very high speed?

regarding the Veyron, the active rear spoiler tilts at 113 degrees, that acts as an Air-brake over 200km/h, in addition to it's disc brakes!

Dragsters and land speed record cars use parachutes.

Here's a big caliper

Hey, you own a Veyron and a M6 and you're asking us about how they stop?

Really! an 8.0L 16 cylinder ( I think that is the one with four turbochargers) 1001 hp .. 7 speed .. 252mph... $1.5 million. I'll take two, a red one and a blue one. Show me where to sign. And where you drive it so I can stay out of your way.