60 fps video lag

or rather than transcoding, you can use a proxy workflow.  It's not particularly intuitive if you run into issues, but it can definitely improve playback of your edit while always returning to your camera original for your exports.  I generally create an ingest preset that matches the frame rate and pixel dimensions of the camera original, but uses something like prores(proxy) as the codec.   And this is the voice of experience speaking, create a proxy for one short clip and see if it works properly before spending a lot of time creating all your proxies.   

There are many reasons why this could be happening. The most common is that the video clips straight out of the GoPro are highly compressed and use a codec that is not friendly to editing Premiere Pro. I always transcode the clips to an editing codec (Apple ProRes or Avid DNxHD) or use a Proxy workflow.

Let's see.... so here is where we guess what your computer is made of... let's start with the basics, is it in a metal case? Does that case have fans? How about buttons and is the power button on top or on the faceplate? ... This could take awhile, or... you could tell us something about your hardware to help us along. 🙂