A tip for learning UML. If you don't understand what is it talking about, just ignore it. There are some concept which is just too complicated and not quite useful. Only pick the concept you like/understand, that is what you will use.

UML is a design language, but not a computer language. You don't need to follow everything in the standard.

That will learn UML in an easier way.

Personally I think UML is worth to learn. Since it could design an architecture with using some common building block that many people know. And those UML tool can draw and manage diagram to save your time.