Stories

I dont know what to do, I am already writing a story yet i want to write so many others to, like i have this picture in my head but i would rather make a movie... you know? Cause it doesnt take as long. Me and my cousin are thinking about writing one together, but i want to finish the one ive already started, the problem is she doesnt know i want to wait and i dont want to tell her. I would like to start one with her but I REALLY want to finish mine first, but its only like 11 pages at the most, so it would still be like a really long time until i could write with her. ..... any suggestions?