Lots of piano players find it difficult to play trills. They're those fast "back-and-forth" movements between two notes also called "shakes" that feature in a lot of the piano repertoire. The trick to playing trills is to relax, not worry about speed and try to give equal emphasis to both notes. You can find out more about how to play trills in my article How To Play Trills on the Piano. There's also a link to the score so you can print it out, play along, or both.