Is it possible to buy a horse from chesnut handy stables outside imperial city?? Is there a quest to get horses back or see if the Orc really ate them

No, it is not possible.

Hehe...

In a new game, talk to the 2 stablehands (topic "Imperial City").

Talk to the Orc Woman in charge of the stables ("Imperial City").

The dialogue is amusing ("Burp!"). It worth backing up a savegame BEFORE you talk to them for the first time. There a several places like this... like before you talk to the Orc Bookseller in Leyawiin for the first time ("Buy a goddamm book already!").

The horse armour pack gives you access to a horse there. I don't have any more more info though.