Transcode 2 audio streams using ffmpeg

I have a movie with 2 audio streams: German in track_2 and English in track_3. I want to copy the video stream (track_1) and transcode both audio streams to AAC.

This code

ffmpeg -i Test.mkv -c:v copy -c:a aac -q:a 1 Test_n.mkv

only transcodes track_2.

What is the correct syntax to transcode both audio streams as I have described?