video lag and not smooth

I have about 40 mins of video with full HD quality recorded by iPhone 5s. I added the video clips to the fotomagico. when I play the video that I made with Fotomagico it is smooth and there is no lag. But when I export the video with any format (I tried most of the formats and resolution) there is lag and it is not smooth.
I am using OS X Yosemite version 10.10.2
Macbook pro retina, late 2013,
Processor: 2.4 GHz Intel Core i5
Memory: 8GB
Could you please help me to export the video which will be smooth with no lag. Thanks

hi, is the 40 min video one single piece or multiple videos?

They are multiple videos all recorded by iPhone 5s default camera.