Here is the full list of all 6 Monuments Flipper: Prologue achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Complete all main quests on the Aqueduct
Complete all tasks in the prologue.
Rebuild the Roman Crane.
Order the parts and build a wooden cantilever.
Complete main task in Old Village.
Find all spear pieces, restore and reassemble.