I'm at the part where you have to sneak into Umbridge's office and change the potion.

I keep tapping the footprints with my stylus, but it still says "you lose". Do I only click the black and white footshapes? what about the red ones?

I'm stuck! What am I supposed to do?!?!?!

HELP!!!!

I am pretty sure (haven't played in awhile) that you only tap the white (or black, whichever they start out as) ones. If you did it right, they go black, if you missed, they go red. I might be getting black & white mixed up. So only tap the white ones! let me know if that doesn't work! (just post it here!)

Hi. You have to tap them in order they show, and quickly on the way in. On the way out a fraction delay is needed, still in order they show. If too quick, Malfoy will hear you and catch you, you have to start again. On way in , quickly tap, on way out, a fracctional delay on footprints (feet). Hope it helps.

I can't seem to do anything but cast spells on chairs or chests. There is no one around so Harry can't talk to anyone for new tasks. I only seem to be going around in circles or getting lost. I know that I'm not finished the game because I'm on Task 28 and only 58% through. But I don't know what to do now, like where do I go to get a new task....???? Help anyone....Please....

Um, I think maybe you should've started a new thread, but I will try to help.
Task 28 might mean you're done...I cannot remember for sure. But have you gone to the Ministry and defeated the death eaters and Voldemort? Afterwards you return to Hogwarts, and no one is there (except the people playing gobstones, exploding snap, etc).
If you're only 58% complete, then that means you still need to find gobstones, chocolate frogs, etc. Also, completing all the games and lessons on the green board in the common room will give you a higher percentage.
If you need any more help, feel free to let me know!