I want to start speed running but I don’t really know how to start off. Like what do I have to do to start and official speed run?

Personally I like to speedrun the games I liked playing. If you want to record your screen you can either use your phone / tablet or a capture card.

*speedrun

Each game is going to have their own categories and sets of rules, and speedrunning on different consoles will change your setup, so you'll have to select a game first.
Generally, runners use timers like LiveSplit while they play, but this is almost never a requirement. If you want a simple setup, just find a way to record your game. If you're on a computer, use OBS; if you're on console, you can purchase a capture card to connect with a computer or just use a phone or external camera to record.

If you're on a computer, use OBS; if you're on console, you can purchase a capture card to connect with a computer or just use a phone or external camera to record. mcdvoice