you prob have issues with your clutch hydraulic system.
i recommend just jacking the rear up the ground to do that test... a little easier on the drivetrain.
basically jack up the rear. put something by the front tires to make sure it won't roll. put the car in 1st gear with your foot firmly on the clutch pedal. start the car. have your buddy check if the rear wheels move. if they do, your clutch is not fully disengaging.
check:
clutch pedal play
fluid level
clutch master clyinder
clutch slave clyinder
etc.
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