Merging changes from upstream master (GitHub)

[FranceBB]

Hi there,
even though I'm an encoder, namely a broadcast engineer, I studied Computer Science Engineering and I do work on some projects as developer as the company asked me to do it in the past. Since pretty much everything I've done is made by myself only, I would rather not lose them if the company kicks me out one day, so I forked it to my personal GitHub account.
As I make changes, I generally get a message on my fork saying that it's "x" commits behind, so I compare it with the master (which I updated myself) and I merge changes to my fork.
Easy peasy.
So I thought: since I rely on Avisynth all the time and I use it as well in some of the automatization programs I made to make my life easier, wouldn't it be bad to fork it and keep it stored and upated in a "safe place" like my Company's GitHub so that if something terribly bad happens to Ferenc, I would still have a safe working copy? So I forked it from https://github.com/AviSynth/AviSynthPlus however, I can't see changes and merge them to my local fork. Why?

[ChaosKing]

Do you see the typical "forked from AviSynth/AviSynthPlus" text under you repo title/name on github?

[FranceBB]

For Avisynth? Not really, no: https://i.imgur.com/cxHQi53.png
However I do see it for other repositories I work on: https://i.imgur.com/AXIuBOe.png

[ChaosKing]

This is why you don't get the x commits behind message. It think this called "git upstream" where you can set up a repo as a parent repo or something like that.
If you click on the fork button on github it sets it up automatically for you.