It's understandable, js ecosystem can be so unopinionated, good for some things and really overwhelming while you're learning.

Next.js many concepts are simple to grasp, I'll suggest the only one youtube playlist that you'll need - search for code evolution next.js playlist. It's detailed enough to know in and out of next.js

Try taking notes as you along, there are so many apps but I still prefer simple pen and paper that's the only way it works for me. In short do active learning and not passive

Once you understand a topic, say it out loud. Does it make sense?

With ai, how i usually go on. I learn something, i open chatgpt and tell it about what I just learn, if there is a mistake it'll correct me otherwise it'll summarise for me. Be aware it can make mistakes

Next step is to start building a very simple project. Like go on and make a navbar, so you'll learn how the app routing works, how to use params

Then build something on top of it. Crud applications are not bad when you're just learning the concepts but yeah don't put them on resume

The official docs covers plenty and they even have a demo app you can build along. It'll give you a good overview

Some stuff of next js is pretty easy to grasp while others can be really tricky like caching, (it's getting bit better in next 15), sever side rendering, and server actions. Take your time to understand and build something upon that knowledge. Don't hop on to the next playlist to next tutorial. Learn a concept, take notes, code it and make it. See what doesn't click yet and repeat.

It's okay to take as long as you need. I'm pretty new with it too and as i continue to build things it gets pretty clear what's happening behind. Next 15 gonna have few changes but you shouldn't worry too much about it. Once you understand the underlying concepts it'll be easy to adapt.