Megan10e

Could someone please help? I'm trying to edit a short video (about 2:30 long) of 49 clips set to a song. I'm working on editing the clips to work with the transitions in the music, but whenever I increase the length of one clip, it decreases the length of the clip after it. Is there a way to set it so that the rest of the clips "move over" when I increase the length of one clip, so the other clips are not affected? Thank you!