video preview is lagging in the adobe premier

You can't compare playback of a video player and an NLE ... the NLE has dramatic requirements for hardware resources going besides stitching together bits & pieces from clips, while the video player just runs a file through the CPU for playback. Not even close.

So the hardware to run a program like PrPro is a lot higher need than to just play videos.

Next ... that media you're using is nasty stuff for an NLE. It's encoded in a very complicated process done by a specialized chip built for that camera to get both size and time to write down to usable levels. It is NOT meant for editing. In GoPro's manual for their (unfortunately discontinued!) Studio program, they had the following:

For that media, most people find using the PrPro proxy process is a huge help, even on computers with far more power than yours. I would suggest ingesting via the Media Browser, using one of the included Cineform proxy presets in PrPro. And do NOT worry about matching frame-sizes, that's unnecessary for proxy work as this is designed .... toggle the proxies on during playback, off when paused to check quality. Using the Toggle Proxies icon found on the menu of additional controls for the Program monitor screen, accessed via the + button on the far right of the program monitor control block.

For currently imported clips, in their bin in the project panel, select, right-click, Proxies/Create Proxies. And wait for them to be created by ME.

Neil