how to change volume of audio at specific time in audio and add that audio to video(with audio) using ffmpeg command?
Use

ffmpeg -i video.mp4 -i audio.mp3 -filter_complex \
"[1:a]volume=150:enable='between(t,10,20)'[1a];[0:a][1a]amerge=inputs=2[a]" \
-map 0:v -map "[a]" -c:v copy -c:a libvorbis -ac 2 -shortest output.mp4