just select first video and first audio stream… no subtitle

ffmpeg -i input.mkv -map 0:v -c:v copy -map 0:a -c:a copy outputfile.mkv

cutting time, you have to set an time marker at which point it will be cut. Example at 0 hour 12 min 16 sec.

ffmpeg -i input.mkv -t 00:12:16 -map 0:v -c:v copy -map 0:a -c:a copy outputfile.mkv

if you have to select all audio and all video streams map flag will be drop and just do

ffmpeg -i input.mkv -t 00:12:16 -c:v copy -c:a copy outputfile.mkv

selecting streams

ffmpeg -i input0 -i input1 -map 1:v:4 -map 0:a:2 -map 0:s:16 -c copy outputfile.mkv

the -map is set right before the outputfile and before the -c copy

-map 1:v:4 select the5th video stream from input1
-map 0:a:2 select the 3rd audio stream from input0
-map 0:s:16 select the 17th subtitle stream from input0