So let's recap how you ot the footage to the device you want to edit or show it on:
There are basicly two options:
a - 1) use the cable that was in the package (the flat one) and connect the drone to your computer, switch on the drone and you will (should) see the drone and the SD card as external devices apear on your computer.
a - 2) take the SD card from the drone and put it into the computer, evt. using an adapter or a SD-Cardreader device, since most computers do not have a slot for the micro-SD-Card
b: Now you move the files you want to a directory on your harddisk and wait untill this is finished
c: you check the footage unedited, the delete the files
After you have done that, you can look at the file size of the footage, giving you an indication of the quality. Roughly said, a minute of footage in 4K will be somewhere between 800 MB and 1 GB. You also can see the size of the screen (at least if you use a mac, this is what it looks like)
this is the raw footage you then import for editing (or if you use FCP, you simply can work with it without importing).
Is this the way you get your videos from the drone?
If you try to look the videos while still on your mobile device used to fly, you probably will see the cache, which is lower quality.