In my opinion, the main thing to learn with the A4 is subtractive synthesis. The A4 is four very well featured monophonic (ish) analog subtractive synths, plus controls for sequencing, assinging the four synths for polyphonic duty, FX and more. If you can wrap your head round a Digitakt, and around synthesis, you’ll be fine with the A4.
If you have the budget for it, Syntorial is a rigorous intro to synthesis: https://www.syntorial.com/
This is the forum’s A4 love-in thread: Isn't the Analog Four the most incredible and deep instrument from Elektron so far? - loads of opinions, example sounds and some helpful techniques discussed there.