Replying to GoPro4 Video Conversion

Okay, i'll start by saying i basically don't know shit when it comes to cameras.

Recently I was filming with my new gopro at 4k 24fps. Once I transferred them to my hard drive, all the shots came out really choppy on the playback. Is there a way to convert them to a smaller frame rate or resolution so I can make them watchable?

I've been playing around with the gopro application on my mac and trying to convert them to 1080p, 720p, etc. but they still look choppy after conversion

Thanks for any help NS