sony vegas pro 13

if anyone is really good with sony vegas pro 13 i would really like some help and if you are able to help me out one on one by emailing me thatd be amazing just let me know cause i am stumped.

Hello so if anyone who reads this is familiar with the iphone 7 4k video and sony vegas i would really like some help. So my problem is that when i put the video into vegas the preview screen is very choppy even when i put the preview quality as low as it goes, is it a problem with my computer...