Very slow playback before editing

I have just installed DaVinci Resolve 17.2.1. and I am new to this software. I can import the MP4 files into Media Pool but when I run the file to do the editing it runs slow and jittering ever 2 seconds. I have checked the file using windows and it runs fine. I have checked the video setting on my Windows 10 pc and my Benq monitor.
The files did come from my Go Pro 8 Black the resolution was 2.7K at 60 fps and were copied direct from the sd card.
Thank you in advance
The files did come from my Go Pro 8 Black the resolution was 2.7K at 60 fps and were copied direct from the sd card.
Thank you in advance