I can not set a timer or i just dont know how to and i want to try speedrunning so i need to know if its a nessicary requirement or if its just so you know how you did at the time of you doing it

Check the rules of the run you are submitting because it will depend. I did a run without a timer and timed it afterwards on my phone's stopwatch and was fine.

My previous two runs didn't require a timer I timed it according to what frame I started the speedrun and what frame I ended it.