Here is the full list of all 20 GESTALT: The Fifth Day achievements.
Find the message from the developer.
Get the good ending to the RATS scenario after choosing to kill them.
Get the good ending to the MOTHER scenario.
Feed every plant the wrong item in the PLANTS scenario.
Complete all of Emma's topics in the EMMA scenario.
Listen to every radio broadcast in the RADIO scenario.
Get every question correct in the TRAINING scenario.
THE FOURTH DAY
Get Ending III.
Get Ending V.
Allow the [???] to grow to its full size during the DRAIN scenario.
Get Ending II.
Get Ending I.
Unlock and activate both secret codes.
Complete all of Emma's topics in the EMMA scenario, get the good ending to the EMMA scenario, and beat Super Emma Mode.
Get the bad ending to every scenario.
Get the good ending to every scenario.
Get Ending II on your first playthrough.
Get every ending.
You found something you shouldn't have.