I can not change IMovie settings from 60 frames per sec down to 30 frames

HI, Vlad6211,

Assuming that you are using iMovie 10, iMovie sets the project resolution and frame rate as that of the first video clip (not photo) placed into a newly created project. You can then delete the first clip if you want. Once the resolution and frame rate are set in a project, they cannot be changed. In other words, you cannot delete the first clip and substitute a new clip with a different resolution and/or frame rate, because that won't change the project resolution and frame rate from what you originally set.

So, to change the project from 60 fps to 30 fps you need to create a new project and insert a known 30 fps video clip, with the resolution that you want, into the project as the very first clip. (You can delete it later). That will set the project at 30 fps. Any 60 fps clips that you later add in will play at 30 fps in the project.

-- Rich