iMovie 9.0.4 not exporting high resolution

I created a video, 20 minutes long on my iMac (high sierra is the highest OS possible), utilizing high resolution photographs, as well as transitions and titling. I exported the project under "Share" as a Movie. It took an hour and a half. The resolution was completely decimated, therefore making the video unusable. It went from a beautiful looking video in the software to junk, with softened photos and noise/discoloring throughout, even with the most beautiful and professional imagery. Also, when I duplicated the project in iMovie to safeguard the work, it did not accurately duplicate it, it provided titles towards the end of the project which were not the most current version of the work. This is a professional project and I need help asap. Thank you.