Here is the full list of all 13 LEGO Builder's Journey achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Learned the basics
Learned to climb
Completed the hike
Went on an adventure
Cleared the puzzles
Found a way in the dark
Made your way through the danger
Went back home
Played with your new friend
Made your way up from the depth
Broke free from the machine
Imagined a way out of the dark
Journey complete