Use map
parameter to select audio streams and copy streams by each stream separately. Example (please don't copy example as is in your command line with comments, you must remove comments first and format it as single line or connect lines breaks with \
symbol!):
ffmpeg -i input.mp4
-map 0:0 -map 0:1 # Include both (2) audio streams
-aspect 16:9 # Change video aspect ratio
-c:v copy # Copy audio codec settings
-c:a copy # Copy audio codec settings
-c:s copy # Copy subtitles
output.mp4
or
ffmpeg -i input.mp4
-map 0:? # Include all audio streams
-aspect 16:9 # Change video aspect ratio
-c:v copy # Copy audio codec settings
-c:a copy # Copy audio codec settings
-c:s copy # Copy subtitles
output.mp4