Pretty dumb question but I don't really know what to use lol.

No such program exists. Mods time runs manually. To help mods and viewers first and most importantly make sure your recording doesn't drop frames. Second, have a timer on screen so it's easier to verify.

It would be really nice to have a livesplit autosplitter :D

i mean to count the time of the video like an editing software

idk how to edit videos :/ I record with OBS, view the recordings with VLC and cut the goods with LosslessCut

useful VLC shortcuts; shift+left arrow to move 3 seconds back and E to go frame by frame

I made this for you :) you better watch it :) or else :)