It probably isn't necessary to understand the erlang syntax outside of how to call erlang functions in elixir. Its fun to learn erlang(the language) but the more important part to understand are the things about the BEAM (the erlang/elixir VM) like..
The Actor Model https://www.youtube.com/watch?v=7erJ1DV_Tlo which will be an intro understanding to the next point..
Processes, Supervisors & Workers http://learnyousomeerlang.com/building-applications-with-otp
learn things like the "let it crash mantra" how that changes why you don't hardly ever see (and shouldn't rely on) try/catches in elixir.
immutable data
ets tables and other types of storage that the BEAM provides by default.
how to spin up/use processes
clustering
These are some of the things that the VM gives you. And some of the architecture that make the patterns you will see in elixir different
then many other languages.