How much body language do you understand?

Can you notice things like when they're uncomfortable, mad or happy?

I'm undiagnosed and unsure, for instance.

I think I can kinda tell some like when people frown means that they're upset or confused. When they smile and their lower lids move up almost like they're squinting, means they are genuinely happy as opposed to when they only smile with their mouth. When they open their eyes wide, means they're scared.

The worst one is when they frown, talk showing their teeth and open their eyes wide is when they're deeply angry.

There's a specific emotion is that when they seem sad. Their shoulders rest down, the corners of their moth go down and they stop talking. Or they talk in a lower and softer tone, with a specific lower inflection at the end. I don't know if they're tired or sad when they, but I know it's probably bad. They don't move their arms a lot, too.

While I can, my understanding of it is kind of limited and I don't always can tell the cause. I'm not sure if my reading is normal or not, but I can kinda tell because I associate the movements with the emotions.

Can you tell those things irl? If so, how much?