in below command final video is created but sound of second video is muted after some time. here duration of audio and video is same.
ffmpeg -y -i intro.mp4 -i videoaction.mp4 -i outro.mp4 -i audio1.mp3 -i vcs-watermark-video.png -filter_complex "[0:v]drawtext=fontfile=FutuMd.ttf: text=helloworld: x=300: y=450: fontsize=40: fontcolor=white: enable='between(t,2,5)',fade=t=out:st=5:d=1,setpts=PTS-STARTPTS[v0]; \
[1:v][4]overlay=W-w-5:H-h-5,fade=t=in:st=0:d=1,fade=t=out:st=63:d=1,setpts=PTS-STARTPTS[v1]; \
[2:v]fade=t=in:st=0:d=1,setpts=PTS-STARTPTS[v2]; \
[3:a]volume=enable='between(t,36,44)':volume=-10dB[3a];[1:a][3a]amix=inputs=2:duration=shortest[maina]; \
[v0][0][v1][maina][v2][2]concat=n=3:v=1:a=1[outv][outa]" -vcodec libx264 -c:a aac -ac 2 -map "[outv]" -map "[outa]" finalvideo.mp4
