If you have problems with iMovie on your Mac, you can post them here. We are users like yourself, and we will help if we can.
If you have problems with iMovie on an iPhone or iPad, you can post your problem at the iMovie for iOS discussions here.
And always, you can contact Apple directly. There is a Contact Us link at the bottom right of this page that should get you to the right place for your country. Calling Apple may result in a fee, depending on how recently you purchased iMovie and whether you have bought Apple Care. They will be able to tell you if there is a fee before charging you.