Hello Evan,
As your mother tongue is Indonesian you need to start by the alphabet and pronunciation as part of an initial basic course to get introduced to the basics of the German language:
Basic words ( greetings ,main verbs, pronouns etc...), basic grammar.
The pronunciation is crucial to know the main differences in pronouncing the letters in German. Later proceed with basic and elementary courses with concentration on grammar rules ,which are quite different and a bit complex.
Good luck:)