What`s wrong with my way of learning Java?

At the moment I'm learning Java. I learned languages before and have some background in IT so far. So I understand core concepts of languages (types, loops and so on) and usually I learned from books. This time I've decided to learn Java through a project. I've watched a video course of Yakov Fain and went through his book before.

My project is a web app, and I`m doing it with Vaadin framework. It seems that it works. I mean I've set a goal and step by step I'm going there, but it seems to me that I still don't understand some core concepts and/or I do it not in a 'conventional' way. Maybe it's all about design patterns (I've never learned it, only heard about it), maybe I should read some "Java cookbook" or something. Or maybe it's the wrong way to learn from a framework (Vaadin helps a lot but at the same time it hides some "guts" of the things from you.

Again, the app works, step by step, but I always think like 'should I do this or that, should I get data from the DB, because it's changing constantly or maybe there is the way to sort of cache it. Then Spring and stuff like that - I have no conventional Backend - because of Vaadin again - so it looks like I'm in a process of inventing of a wheel. Sounds messy probably, but that's the point I'm at the moment. Very messy and frustrated.

Any ideas? Thanks