Of any calisthenics exercise, pull-ups are the most difficult to perform and see improvements without significant time and effort. Your pulling muscles (biceps, latissimus dorsi, rear deltoids, ...
Ahhh, that first pull-up feeling. I’d say it took me about two years from knowing what a pull-up was to being able to do one, which sort of just…happened, in September 2020, on my home pull-up bar.