I was in stealth shooting arrows into its face it took like 7 critcial stealth hits before it died .-.

but how do i have this horse again ?

7 stealth shots well the horse is quite durable then, good to know and start a new game if you want it back or if you know the console command code.

LOL I think this is the first post whereby

"I spammed shots into my horse and it died, how do i get it to live again?"

Reload a save would be the easiest, if not you probably can't resurrect it by playing the game normally i think. Don't think it respawns,

Shadowmere will respawn where she died; according to the UESP, it takes 15-20 days.

k so ima have to avoid dawnstar for ages .-.

(i killed it because i wanted to figure out how to make it live in the event it should die on me since i know this horse to not truly die like evry otehr horse in the game would stay dead)

(also have 87 archery at minimal critical hit perk 1/3 deadric bow legendary smithed and steel arrows + 87 sneak and teh sneaky archery perk thing)

This. ^

Make sure you know exactly where he died though.