I would start with your video settings. Are you caching locally to your device? If so, turn that option off. You don't really need it as the video on the card in the camera far superior in quality.
That is very normal. The phantoms are not racing drones, so a little bit of lag is fine, I rarely notice it. Try clapping in front of the camera while watching the video feed, it is slightly delayed. Drones with lightbridge have a little less delay, but the standard can't transmit video over WiFi very well. You could try using a better device, that might help. I upgraded from my cheap Android phone to an iPad for running DJI GO, and I noticed a bit of a performance increase, but a bit of video lag is still present even after upgrading to an expensive tablet. There's really no way around the lag, but don't worry, you'll get used to it. (I would recommend using an apple or Android tablet of 10 inches or more if you are not already using one, it makes a big difference in performance and the fact that you can actually SEE what you are filming!) Have fun and fly safe! [emoji6]