First BeeGee, welcome to the forum - glad you found us. Hope you can visit more and even help us out from time to time too. While most of us (all in the US) cannot even get a clutch, I'll offer some experience and opinions anyway. I don't know where you're from so i will comment on costs in terms of what typically to expect in the US, and perhaps another member can chime in on the same from where you are.
Second, it does sound like a clutch master (you have no slave) cylinder failure, BUT I hardly imagine that means clutch (3 parts, disc, pressure plate and throw-out bearing) replacement is necessary - AND even if THAT is true, I'd be suspect that the flywheel necessarily needs replacement as well. It sounds to me like your garage is setting you up for a nice big bill. Anyway, I have no idea how much distance, age and type (city/highway) driving has been done with this car - ALL of which go into the equation for expectations, but regardless will try to give you an idea of costs more or less by ala carte.
A clutch master cylinder - parts about USD160; labor - installation, hydraulic flush and top off - USD300
Clutch itself - these three parts, disc, pressure plate and throw out bearing ARE usually put in together, but you may be able to skip the pressure plate, and you may need to add a pilot bearing. Anyway, parts are about USD650, and labor for installation is prolly around USD600 too.
IF you need a flywheel - and there's a better chance you could just need a resurfacing of it, parts are about USD800 and labor installation about USD200 (provided the clutch labor is being done at the same time, otherwise count on USD600 just for it. btw, flywheel resurfacing is around USD100-200.
...hope this helps a bit - not a small job, really -
Garage changed the master cylinder got the car back today
Did 5 miles and the problem happened again clutch pedal to
The floor anyone know What else the problem can ? Also
Is it a common fault on this car !
No to the common fault - this is a hydraulics issue - and it sounds to me like the repair didn't go correctly. When the pedal sinks to the floor, it's because the hydraulics have failed - prolly leaked past a faulty, worn or blown seal. If this happens on a new master cylinder - new seals, piston etc. - then there's simply a massive leak somewhere - perhaps at the very connection to the master cylinder or to the connection at the clutch. It could (but I doubt it) be a bent, broken kinked line too - anywhere the line could've been damaged so that the fluid leaks out.
It's also possible that the tech didn't attached the hydraulic line to the new master cylinder completely or correctly - but he SHOULD have noticed this upon refilling the systems and bleeding air out it - it should've failed right then. Lets us know what the official verdict is ...