I have a question about the infamous "Sacking of the Imperial City" or rather about what that is happening afterwards.

I wonder if the city is in ruins or if they have started to rebuild?
And what of the elder council, did they get killed, did they survive or have the Aldmeri Dominion made a new one?

I have tried to search the different lore wikis and such but that came up with nothing.
I would be really thankfull for any answers!

It's not in ruins. A moth priest from Dawnguard mentions in his dialogue that moth priests and the emperor still live in the white tower. He did say that the tower isn't what it used to be as it got damaged in the war.

thanks for the info merewolf! so they are most likely rebuilding. but what of the elder council, anyone know anything about their state?

they probably evacuated the council and moved them north when the city became in direct danger. after the war it would only make sense they moved back in same as the emperor did

We really don't know what happened to the Elder Council other than it/part of it possibly planning a coup, based on Amaund Motierre's actions in Skyrim.

I wouldn't be surprised if the Thalmor replaced half of it with pro-Dominions.