Here is the full list of all 17 Backrooms Break achievements.
Theseus would be proud
We need to go deeper
Acquired the shotgun
Acquired the sniper rifle
Kill the invisible monster
..or is it?
Found the elevator
Acquired first gun
Acquired the assault rifle
Died for the first time
Found the gun cabinet key
Hopefully it's almond water
Found first weapon attachment
How do I get out of this place?
Get a first kill
Escorted the ball into the elevator
Break all the walls in Level 0