Ask HN: How can I learn human psychology?

I want to understand how humans think. Mostly to help me make software products more understandable to more people (usability and UX), also to fathom solutions to problems like climate change (which I think are now primarily psychological problems), and also to understand my own psychology to better harness my potential.

I have no background in psychology. I am a software engineer and team leader in a successful 50-person software company. I have been interested in how other people think only for a few years. "How to win friends and influence people" was very influential for me.

After thirty-something years I think I understand my own psychology pretty well. At least, I no longer find it deeply interesting. I am acutely aware that I am just one example of humans, and I am not like others; If you could measure individual's psychologies in a single dimension, I think my own psychology would be just outside the standard deviation.

I tried reading about Freud's id, ego and super-ego on Wikipedia, but quickly realised I had thrown myself in the deep end.

Where is a good place for me to start learning about human psychology?