How do i highlight or delete a speedrun if i submitted 2 runs by accident?

did you submit one video with two runs in it?

If you’re saying that you submitted a run but it went through twice, then go to your pending actions, select one of them, and click the three dots to delete it.

It's also pretty obvious for the mods when there's duplicate submissions. Deleting one yourself is courteous, but it's just a few clicks and keystrokes to reject one on the mod's side as a duplicate submission. So either way, no big deal.