I had done a few design courses at college and later online. Most of what I’ve learned comes from the 2 years I spent at Directi. 

Every interaction design decision needed to get justified. Even small product decisions were debated.

I remember arguing with a designer about the optimal number of participants to get feedback from before the insights started to repeat themselves. Watched the CEO argue with another designer about whether the icon for menu expansion should be → or ↓.

I was forced to learn Sketch by my manager Madhur. He was not happy with Balsimiq mockups. 

It is funny that I learned Sketch not through the design of features, but through creation of memes.

By the end of my 2 years, I had probably read most of the posts on Nielsen Norman Group’s blog. (It’s great, by the way).

My advice is to have a period of time where you are obsessed with one aspect of product management: be it design, engineering, data or strategy. You will come out of it a much better product manager than if you try to learn it all at once.