I realized I couldn't stay in a squating position with my feet flat for more than a few seconds, yet you can see those Asians and Africans using this position instead of sitting.
Do you have any advice on how to learn it? What kind of exercises should I do, what do I lack or have weak that I can't do it?
Get rid of the chairs, etc., in your house, and squat a lot, your muscles and tendons will adapt.
chances are you have limited ankle mobility and maybe tightness in other areas (hips, lower back, lats). Practice getting into a deep squat position while holding onto a pole, door handle etc.. It worked for me