Welcome to the forum!
I Have about 10 days of free time to really get up to speed with the language and ecosystem before I embark upon beginning to build a side project with phoenix.
The course is a good quick start but I think you should be seriously considering:
- Elixir in Action 2e (to get the “process thinking”)
- Programming Phoenix 1.4
- Programming Ecto (you’ll likely be interacting with a database like PostgreSQL)
Won’t finish that in 10 days though …