After changing clutch kit it takes a long time to accelerate

I would double check that the clutch was the correct one as that sounds like the clutch is barely engaging. How much free play is at the pedal?
Going by the image you adjust the pedal to these various dimensions.

Clutch pedal height, dimension "H", 9.29-9.69 inches.

Clutch pedal stopper bracket clearance 0.012-0.039 inch with pedal fully depressed.

Clutch pedal freeplay, dimension "A". 0.039-0.059 inch. Clutch pedal freeplay is adjusted by rotating the clutch master cylinder pushrod in or out until you are within the specified distance. Then tighten the locknut.
Once you complete those adjustment pump the clutch a few times and verify the dimensions are still correct. If the clutch is still slipping then you will want to bleed the system. If still not engaging you will probably need to pull the transmission and check for parts that are binding or wrong.