Here is the full list of all 23 Gnomes Garden 2 achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
For defeating the wicked witch
For completing all levels with 3 stars
For collecting all trophies
For getting the sixth seed
For getting the seventh seed
For getting the fifth seed
For getting the fourth seed
For growing a lily pad
For getting the third seed
For stopping time
For activating an altar
For completing 15 levels with 3 stars
For speeding up construction
For restoring the signal fires
For getting the second seed
For getting rid of a Merrymaker
For restoring Stonehenge
For getting the first seed
For speeding up workers
For completing 5 levels with 3 stars
For restoring a plant
For constructing a building
For clearing one roadblock