Do you already know what languages are in your program curriculum? You should see if you can find out. I’m guessing it’ll be a mix of some object-oriented language (C++/Java), maybe some functional (OCaml, Haskell), and some assembly. You should consider writing to your advisor or find some upper-class colleagues that know what the path looks like.
Additionally it’s incredibly useful to learn how to use unix/linux, git, docker, regular expressions and other like things of that nature.
As for your mobile development question, for android the common languages are Java and Kotlin, for mac it’s swift mainly.