In imovie, mp4 file optimizing taking too long. How can I quit/cancel without losing the current project?

Please help! Thank you! This is my first project and the deadline is coming up fast I need to pick a different mp4 to optimize because the one i am doing now is going to take 10 more hours. I cant wait but I already am halfway done with the project using severel clips from other mp4s but havent saved. Is there anyway to quit or cancel the current optimization without losing all my work?