I'm completely stuck in Harry Potter and the Chamber of Secrets

At the moment it feels like I'm playing a game of stuck in the mud with the teachers and I'm the one always getting stuck. Every things gone hunkey dorey until now I get to the point when you have to stand on a pressure pad before time runs out but Snapes always catching me either that or I run out of time and its driving me please help

PS I'm new so cut me some slack!!

Yeah, i got stuck on that the first time i did it, before you run to the pressure pad, wait at the bush so you can still see snape, wait for him to go off to the left of the screen, quickly run and get on the pressure pad and run back and out through the gate, you have a time limit, so speed is the key to that.