I did speedrun but obs got my recording as a black screen and no sound. I remember how many minutes I finished but I don't remember how many seconds. I also have a demo recording. What can I do?

You can play the demo by typing in the console - playdemo (name of the demo that you recorded) - and count the seconds with the timer of BunnyMod XT or count with a stopwatch or let the moderators correct it for you.