please help me!!

All the letters fall down if you make a mistake - if it's happening even though you haven't made a mistake, it may just be that the game is glitching.
During the beta trial they had a ton of problems with the dueling and it was shut down for over a month.

To play properly you have to either click on the letters or press them on your keyboard at the right time (as the white line hits the next letter). To gain power you want to click or press the letter just as the white circle swells to it's largest size around the letter. Keep practicing, you'll get it!