Can I do speedruns if I am 11?
Yes you can speedrun, absolutely.
However, the privacy policy of this website (all the way at the bottom of every speedrun.com page) mentions: [quote]Individuals under the age of 13 should not use speedrun.com.[/quote]
This doesn't mean that you cannot do the act of speedrunning of course. Start a game together with a timer and zoomie zoomie.
(The keyword is should: Should probably ask your parents or guardians about you visiting this website/showing them the privacy policy).