I'm really sad that Signal Ops didn't return. I missed its sale on the first day, then it apparently vanished.

No.
At the moment all of the daily bundles have returned, but not the daily deals.
I expect that in 20 hours, the deals will return too.

Divinity Original Sin is no longer sold on GOG.
Divinity Original Sin Enhanced Edition was never part of this sale.

It might still appear tomorrow. Crossing my fingers for you.

I want to buy Crimsonland but my wallet is empty. So do you mean I have only 24H (until tomorrow before day 11) to buy it? Because it appeared in day 10 again. I guess I will miss it.

No.
I can't be sure, but I believe you have 48 hours to buy Crimsonland, because if you had only 24 hours it would be marked as "Last Chance" (like the Pillars of Eternity games) and it is not.

Okay. I hope I can buy it. Thanks for the help. :)

Check your chat.
Welcome to GOG and thank you for listing yourself in the directory of public wishlists.

12 Hours Deals - Round 18

Witcher -85%(1.49)
Witcher 2 -85%(2.99)
Witcher 3 Wild Hunt - 30%(41.99)
Witcher 3 Wild Hunt: Hearts of Stone -10%(8.99)
Master of Orion 1+2 -75%(1.49)
Legend of Grimrock -85%(2.29)
Legend of Grimrock 2 -75%(5.99)
Master of Magic -75%(1.49)
Nox -75%(1.49)
Blood -75%(1.49)
Blood 2 -75%(1.49)
Jade Empire -80%(2.99)
Jagged Alliance -75%(1.49)
Jagged Alliance 2 -75%(2.49)
Fahrenheit -60%(2.39)
Resonance -80%(1.99)
Age of Wonders -75%(1.49)
Age of Wonders 2: The Wizard's Throne -75%(2.49)
Age of Wonders Shadow Magic -75%(2.49)
Age of Wonders 3 Deluxe Edition -75%(11.29)
Age of Wonders 3 Eternal Lords -33%(13.39)
Age of Wonders 3 Golden Realms -33%(7.99)
Little Big Adventure -80%(1.19)
Little Big Adventure 2 -80%(1.19)
Gemini Rue -80%(1.99)
Grim Fandango Remastered -66%(5.09)
Syberia -80%(1.99)
Syberia 2 -80%(1.99)
Medal of Honor: Allied Assault War Chest -75%(2.49)
Clive Barker's Undying -75%(1.49)
Sacred -80%(1.99)
Sacred 2 -80%(2.99)
Capitalism -75%(1.49)
Capitalism 2 -80%(1.99)
Bard's Tale -80%(1.99)
Pillars of Eternity Hero Edition -50%(22.49) [LAST CHANCE]
Pillars of Eternity Champion Edition -50%(29.99) [LAST CHANCE]
Pillars of Eternity Royal Edition -50%(44.99) [LAST CHANCE]
Blitzkrieg -80%(1.19)
Blitzkrieg 2 -80%(1.19)
Cannon Fodder -75%(1.49)
Cannon Fodder 2 -75%(1.49)
Rogue Legacy -80%(2.99)
Haegemonia -80%(1.99)
Rise of the Triad 2013 -60%(5.99)
Robin Hood -80%(1.99)
Galactic Civilizations -80%(1.99)
Stacking -85%(1.49)
Grid -50%(7.49)
Sir, You are Being Hunted -85%(2.99)
The Last Federation -50%(9.99)
The Last Federation: Betrayed Hope -50%(3.49)
The Last Federation: Lost Technologies -10%(6.29)
The Last Federation Collection -50%(12.49)
Broken Age -75%(6.29)
Ring Runner -80%(1.99)
Halfway -70%(3.89)
Screamer -75%(1.49)
Screamer 2 -75%(1.49)
Battle Worlds: Kronos -80%(3.99)
Rogue Trooper -50%(4.99)
Strike Suit Zero -85(2.99)
Men of War -80%(1.19)
Men of War: Assault Squad -80%(2.99)
Men of War: Red Tide -80%(1.19)
Men of War: Vietnam -80%(2.99)
Crimsonland -80%(2.79)
Dead State -66%(10.19)
Zombie Shooter -80%(1.19)
Zombie Shooter 2 -80%(1.19)
Star Ruler 2 -60%(9.99)
Ether One -40%(11.99)
Ether One Deluxe Edition -40%(17.99)
Entomorph -75%(1.49)
Invisible Inc -50%(9.99)
Invisible Inc: Contingency Plan -10%(4.49)
Braveland -74%(1.29)
Braveland Wizard -74%(1.79)
Braveland Pirate - 26%(5.19)
Lego Batman -75%(3.79)
Lego Harry Potter: Years 1-4 -75%(4.99)
Lego Harry Potter: Years 5-7 -75%(4.99)
Super Puzzle Platformer Deluxe -80%(1.59)
Revolver360 Re:Actor -80%(1.99)
A Story About My Uncle -80%(2.59)
Crypt of the Necrodancer -50%(7.49)
Infested Planet -75%(3.79)
Massive Assault -75%(2.49)
Massive Assault: Phantom Renaissance -75%(2.49)
D4: Dark Dreams Don't Die -35%(9.69)
D4: Dark Dreams Don't Die Deluxe Edition -35%(19.49)
D4: Dark Dreams Don't Die Deluxe Upgrade -35%(10.49)
Pixel Piracy -80%(1.99)
Never Alone -67%(5.89)
Celestian Tales: Old North -60%(5.19)
Windforge -80%(2.99)
Subject 13 -75%(4.99)
SuperPower 2 -75%(2.49)
Runestone Keeper -60%(3.99)
Dungeons 2 -65%(13.99)
Dungeons 2: A Chance of Dragons -50%(1.99)
Dungeons 2: A Song of Sand and Fire -50%(1.99)
Dungeons 2: A Game of Winter -15%(12.69)

You made me very happy. I appreciate it. Such a good community. Thank you very much.

Long before the Summer sale, we still have the Winter sale next month (historically the largest sale of the year) and a host of smaller sales (insomnia? mutator? pinata?) in the first half of 2016.

12 Hours Deals - Round 19 (during this round, all the items from Round 1: Part 1, Part 2 made a return, except for the following)

Legend of Heroes: Trails in the Sky -50%(9.99)
Soulbringer -75%(1.49)
Gone Home -75%(4.99)
Spacechem -90%(0.99)
Ironclad Tactics Deluxe Edition -75%(3.79)
TIS-100 -50%(3.49)
Infinfactory -50%(12.49)
Ethan Meteor Hunter -85%(1.49)
Rayman Origins -75%(4.99) [last chance was announced during Round 14]
Assassin's Creed -75%(4.99) [last chance was announced during Round 13]
Farcry -75%(2.49) [last chance was announced during Round 16]
Farcry 2 -75%(2.49) [last chance was announced during Round 16]
Screamer -75%(1.49)
Screamer 2 -75%(1.49)
Hyperdimension Neptunia Re;Birth1 -50%(14.99)
Hyperdimension Neptunia Re;Birth1 DLC Pack -50%(2.97)
Pillars of Eternity Hero Edition -50%(22.49) [last chance was announced during Round 18]
Pillars of Eternity Champion Edition -50%(29.99) [last chance was announced during Round 18]
Pillars of Eternity Royal Edition -50%(44.99) [last chance was announced during Round 18]
Pixel Piracy -80%(1.99)

Thanks. Important list.
Glad I bought Ironclad Tactics on day 1.

I also added to the OP the items that appeared only once during the sale.

Daily Bundles - Day 11

Shooters Supreme - 50% off separately, 66% with bundle completion
Doom - 2.99(1.99)
Doom 2 - 4.99(3.33)
Quake - 4.99(3.33)
Quake 2 - 4.99(3.33)
Quake 3 - 9.99(6.59)
Wolfenstein 3D + Spear of Destiny - 4.99(3.33)
Return to Castle Wolfenstein - 4.99(3.33)

Elder Scrolls Classics - 50% off separately, 66% with bundle completion
Morrowind - 9.99 (6.59)
Battlespire - 2.99 (1.99)
Redguard - 2.99 (1.99)

Fallout Originals - 50% off separately, 66% with bundle completion
Fallout - 4.99 (3.33)
Fallout 2 - 4.99 (3.33)
Fallout Tactics - 4.99 (3.33)

D&D Remade - 50% off separately, 66% with bundle completion
Baldur's Gate: Enhanced Edition - 9.99(6.66)
Baldur's Gate 2: Enhanced Edition - 9.99(6.66)
Icewind Dale: Enhanced Edition - 9.99(6.66)

Classic X Pack - 50% off separately, 75% with bundle completion
X: Gold - 4.99(2.49)
X2: The Threat - 4.99(2.49)
X3: Reunion - 4.99(2.49)
X3: Terran War Pack - 9.99(4.99)

El Presidente Collection - 60% off separately, 80% with bundle completion
Tropico 1+2 - 2.39(1.19)
Tropico 3 - 5.99(2.99)
Tropico 4 - 7.99(3.99)
Tropico 4: Complete DLC Pack - 7.99(3.99)
Tropico 5 - 15.99(7.99)

Ys Saga - 50% off separately, 70% with bundle completion
Ys Origin - 9.99(5.99)
Ys 1+2: Chronicles - 7.49(4.49)
Ys 3: The Oath in Felghana - 7.49(4.49)
Ys 4: The Ark of Napishtim - 9.99(5.99)

Daedalic: Build your Own Bundle - 50% off separately(75% off 3 games, 80% off 4 games, 85% off 5 or more games, already owned games count towards the bonus you get)
Deponia
Deponia 2
Deponia 3
Dark Eye: Chains of Satinav
Whispered World
Memoria
1954 Alcatraz
Blackguards
Journey of a Roach
Edna & Harvey: Harvey's New Eyes
Edna & Harvey: The Breakout
Gomo
Blackguards 2
The Last Tinker: City of Colors
A New Beginning