Cool...have fun. !!!
I don't wanna spoil the game for you, and give you a wiki page to read.
However, i say this:
Except the main quest you allready finished there are:
>>> SKYRIM <<<
The Companions Quests (Faction)
The Companions - Radiant Quests
The College of Winterhold Quests
The College of Winterhold - Radiant Quests
The College of Winterhold - Apprentice Radiant Quests
The College of Winterhold - Ritual Spell Radiant Quests
Thieves Guild Quests
Thieves Guild - Radiant Quests
Thieves Guild - City Influence Quests
Thieves Guild - Leadership Quest
Thieves Guild - Extra Quests
The Dark Brotherhood Quests
Dark Brotherhood - Side Contracts
Dark Brotherhood - Radiant Quests
Civil War Quests - Imperial Legion
Civil War Quests - Stormcloaks
Daedric Quests
The Greybeards Quests
The Blades Quests
The Bards College Quests
Temple Quests
Side Quests
Dungeon Quests and Other Activities
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>>> DRAGONBORN <<<
Main Quests
Black Book quests
Raven Rock quests
Skaal Village quests
Tel Mithryn quests
Thirsk quests
Other quests
Miscellaneous quests
Expanded quests
>>> DAWNGUARD <<<
Main quests
Faction side quests (Dawnguard side quests / Vampire side quests)
Other side quests
>>> HEARTHFIRE <<<
Create a living home
With this official add-on to The Elder Scrolls V: Skyrim, you can purchase land and build your own home from the ground up.
From a simple one-room cottage to a sprawling compound complete with an armory, alchemy laboratory, stable, garden, and more.
Use all-new tools like the drafting table and carpenter's workbench to transform quarried stone, clay, and sawn logs into structures and furnishings.
Even transform your house into a home by adopting children.
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There are "hundreds of hours of content" to play with.
So, something goes wrong with your first gameplay. !!!
Ahh forgotten to say, you can play as a Vampire Lord or a Werewolf as well...
So sit back and ENJOY the ride...