Octavia clutch releases too slow.

Hi, I have a 2013 Octavia 2.0 diesel 6s manual which was sitting for two years, got it back on the road 2months back and the car has recently got a new clutch release bearing as the old one had leaked. Ever since it has developed this problem where the clutch pedal is taking its own time to spring back up and it's really slow, I can't change gears swiftly due to this because the car revs and jerks really hard if I try to do so. The mechanic said that it'll get back to normal after a bit of driving and it has been a week and about 1000kms and it still hasn't gotten back to normal, today I bled all the air out of the system using a vacuum bleeder and still no luck. The car runs fine clutch doesn't slip, spins the wheels in 2nd gear too when I just mash the throttle but can't shift gears quickly. Some expert advice as to what the issue and fix could be would be really appreciated,  Thank You.