thehellboy So does this mean that i have to login on the playstore and download the official android auto app from there?
The answer is no, you do not.
thehellboy "In order to show up in the Android Auto car interface, apps have to be installed from the Play Store and include Android Auto support."
This is not related to getting your car to use the Android Auto UI, but in relation to apps you may want to use with Android Auto such as Music streaming apps, navigation apps, and Messaging apps.
Spotify from the Google Play store has native support for using the Android Auto UI to play music. Apps downloaded from other sources like Outertune, an open source music streaming app downloaded from Github, requires enabling the dev options located within the Android Auto settings and and toggling Allow Unknown Sources.