cutting out ?

hi i got car last saturday, boyfriend said it fine when he drives but it keeps stalling when slow down at juctions or roundabouts when i drive the clutch is alot stiffer then car i used to drive and it twice flashed stop when slowed down but then reved engine and was ok again, i dont know if there a problem with it or just me stalling as new to the car and then i panick and cant start engine once stall if got drivers behind beeping