First of all I'd be happy to hear your feedback about the course (both positive and negative). Create an issue here in GitHub and share your feelings there.
Now, what do you need to learn next? There are 3 directions that you can take:
- Technology - learn it even deeper. Network, CPU and concurrency, databases, Linux, some specific technology, OOP and testing, Security, UX & UI, etc.
- Processes - Lean, Theory of Constraints, Continuous Integration, Continuous Delivery, DevOps.
- Domain - banking, e-commerce, science, pick one and stick with it.
You should work your way at least in 2 directions here. For most people I'd guess that Technology & Domain would be the default.
But no matter what you choose - you should start getting very deep into the topics. You need to become a go-to person for people around on some specific topics. There are plenty of folks who know a little about everything - this is not completely useless, but it's not particularly helpful either. You need to go further and become an expert in something specific.
Last but certainly not least: a grown up developer is proud of products that he builds - not technologies that he uses.