How to get all endings and achievements? Here's a quick rundown.

1. HUMANITY PREVAILS
Win at the Simon minigame when trying to buy a drink from the vending machine. There's a string of 10 button pushes; every round adds 2, so you need to pass the game 5 times. 

2. PRINCE CONSORT
Go with the Mother; when asked, choose an option I would love to, Mother. 

3. ONE THOUSAND AND ONE FACES
Go with the Crone: don't believe her twice, choose an option But every human life is unique and then Lead the way.

4. THE COVENANT OF COVENS
Go with the Maiden: choose an option Your sisters are probably tired of waiting for you and then I would love to.

5. THE WARRIOR
The answer to the Mother doesn't matter.
Get angry at the Crone (when the Narrator asks Does it make you angry?, choose Yes) , then tell the Maiden Your sisters are probably tired of waiting for you.

6. THE FATHER
The answer to the Crone doesn't matter. 
Encourage the Mother to search for a childe (I am not the child you’re looking for.), then tell the Maiden to stay with her family (Your grandson probably wants his Christmas present.)

7. THE SAGE
The answer to the Maiden doesn't matter. 
Protect humanity by discouraging the Mother (A curse should die out and not be spread further.), then tell the Crone that every human life is unique (But every human life is unique).

8. THE HUMAN
Failing to get any other ending will automatically grant this one.

9. THE HORNED GOD
Achieving the Warrior, the Father, the Sage and the Human ending, restarting the game and going through it to the point of meeting the Narrator witll automatically lead to this ending.

10. I'VE SEEN ALL OF BERLIN
Obtaining all other achievements will grant this one automatically.

If you're having troubles unlocking any of the achievements, try to redownload the most updated version of the game (current most up-to-date patch is 1.01)