Parrot playing, I do that but I’m only able to play that song and not really improvise much. Any ideas?
If you want to learn improvisation it helps to also investigate "why" - why this particular rhythmic figure (e.g as shown in the OP article), why this chord voicing (e.g. block chords? Quartal harmony? Drop-2?), why this melody (e.g. ascending or descending? Arpeggiating the chords or "playing outside"?) etc etc
Edit: One more thing: it's OK to improvise with the help of something like iReal Pro, but nothing replaces improvising with real humans, find a group of like minded people that would like to play with you
As an aside, music skill (and many other skills) can be divided into Reading and Writing. Reading consists of either actually reading sheet music, or Playing by Ear. Writing is executing what is in your mind. In the context of improvisation, it's coming up with those things to execute in the first place.
To be honest, I am a good Reader, but a poor Writer myself, and still in the beginning of this part of my journey. I love listening to jazz, and playing along, but devising my own melodies is almost beyond the current me. But what's great about music is that every day you practice is one that you get better.
(Okay, technically a song is a pattern. But it's a really nice one.)
Seriously though, you can think of melody and etc as relative parts of a scale as well as intervals between notes. Ear training using scales is simplest and eventually starts to apply to more complicated patterns. Eventually you recognize the intervals and scales even if you are not consciously thinking about the descriptors like 'oh this is a major third interval'
First you familiarize yourself with an interval, by just playing it all over your instrument, listening and singing it.
Then you test your recall: Play a note N, and try to sing N+I (where I is the interval).
Once you know more than one interval, you can also test recognition: Someone else plays an interval (N,N+I) and you try to identify I.
Once you've got the twelve intervals (you can go past the octave but that's pretty easy so basically there are only 12 to learn) you can do similarly for chords. Chords are also easy compared to intervals, though, because they are built up from intervals, so even before you can recognize them all at once, you'll already have the ability to pick them apart note by note to figure out what they are.