The quickest and easiest way to transfer data between your Fairphone 3 and other devices is to do it wirelessly. You can use Wi-Fi or Bluetooth to do this.
The link to Wi-Fi doesn’t explain how to transfer files over wifi, and the rest of the article goes on to explain how to transfer files via cable. How does one transfer data over wifi?
Obviously I’m a dog and have no idea what I’m doing, because it’s so easy! /s
If you are referring to https://support.fairphone.com/hc/en-us/articles/360032389072 … then it states there “To know more about data-transfer, please read our other support pages.”, which leads here …
https://support.fairphone.com/hc/en-us/articles/360033075811
… where WiFi is used to access Google’s means of transferring data. Other than that, it says
"If you can not or do not want to use the Google cloud, you will have to transfer your personal data files by hand, via:
USB is the quickest and reliable way. Today I was trying to backup files to drive but gave up, as it was stuck in the preparing to upload loop. I’m really against cloud memory at least in the foreseeable future while the infrastructure is still young, for it to work it has to rely on too many things to go right, and you don’t want to overwhelm yourself with all the unnecessary workarounds, just not worth your time.
I agree, most convenient and reliable as I know it.
Oh how wrong you are here, it looks like there are people out there specifically seeking for the trouble.
Ahh crap, I guess I was too impatient while reading. Not looking for trouble, @Patrick1 
I still think the first article is misleading, but maybe I’m just weird for wanting to transfer individual files and not having everything cloud-based. ;p